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optics | Optics for projecting OLED screen DLP style | https://physics.stackexchange.com/questions/68609/optics-for-projecting-oled-screen-dlp-style | <p>I just bought a small <a href="https://www.sparkfun.com/products/11676" rel="nofollow">OLED screen</a> and was wondering is it possible to make a screen surface a little bit bigger ( 2x ) by projecting it through some optics on translucent surface. It reminds me of viewfinders in some old cameras or SLR lens adapter... | <p>I'll compare the projector to the more appealing magnifying screen. A simplified approach would put a lens with low distortion within its field of view (<a href="https://en.wikipedia.org/wiki/Angle_of_view" rel="nofollow noreferrer">FOV</a>) at a specific distance to the screen. Luckily these screen magnifiers are <... | 700 |
optics | Transmission vs reflection grating | https://physics.stackexchange.com/questions/70353/transmission-vs-reflection-grating | <p>What are the advantages/disadvantages of a transmission vs a reflection grating? It seems like a transmission grating would be easiest to use. I'm trying to get a spectrum from Thomson scattered light in a plasma. The broader the spectrum of the scattered light, the hotter the plasma. It's a weak effect, so it's im... | <p>Transmission gratings are less sensitive to polarization and alignment, but cannot transmit at higher wavelengths (ie typically ~2000nm). </p>
| 701 |
optics | What is the optical illusion called where our sun seems to disappear from view and then rise on the third day? And where can it be viewed from? | https://physics.stackexchange.com/questions/71735/what-is-the-optical-illusion-called-where-our-sun-seems-to-disappear-from-view-a | <p>What is the optical illusion called where our sun seems to disappear for 3 days and then rise again into view on the third day? And where can it be viewed from?</p>
| <p>I do not know about optical illusions but there are 72 hour nights (refraction taken into account) by coincidence in 72 degrees <a href="http://encyclopedia2.thefreedictionary.com/Polar+Night" rel="nofollow noreferrer">latitude</a>.</p>
<blockquote>
<p>Polar Night</p>
<p>a night lasting more than 24 hours, occurring... | 702 |
optics | Vibrations after polarization of light | https://physics.stackexchange.com/questions/72404/vibrations-after-polarization-of-light | <p>When we polarize a light, do we get electric vibrations, magnetic vibrations or the mixture of both. </p>
<p>If both, then how can both electric and magnetic vibrations occur in single plane because polarization actually means to confine these vibrations into one plane?</p>
| <p>The plane of polarization refers to the plane in which the electric field oscillates. The magnetic field oscillates perpendicular to the electric field, and also perpendicular to the direction of propagation (assuming we are talking about a plane wave here.)</p>
| 703 |
optics | Is there any optical phenomenon can't be explained without magnetic field? | https://physics.stackexchange.com/questions/72494/is-there-any-optical-phenomenon-cant-be-explained-without-magnetic-field | <p>Almost all optical phenomenon can be explained considering a fluctuating electric field. Is there any optical phenomenon which can't be explained without considering two fluctuating fields, electric and magnetic?</p>
| <p>As you say, almost everything optical can be explained through the electric field. Lets say you just have a plane wave traveling in the k direction:</p>
<p>$$E_0e^{ikx}e^{-i\omega t} \hat E$$
Where $\hat E$ depends on the polarization. What we see or what we record in optics is Intensity, which is $|\Phi_{TOT}(x,... | 704 |
optics | Rayleigh scattering in three dimensions | https://physics.stackexchange.com/questions/72938/rayleigh-scattering-in-three-dimensions | <p>How does the Rayleigh scattering intensity depend on the polarization angle of the incident, linearly polarized light, and the observation angle in three dimensions?</p>
| <p>In short, Rayleigh scattering is like ideal dipole radiation: the radiation pattern for Rayleigh scattering is exactly the same as dipole radiation when the light is perfectly and linearly polarised, so that the intensity has a $(\cos(\theta))^2$ dependence. For natural, randomly polarised light (e.g. from the Sun),... | 705 |
optics | A simple question | https://physics.stackexchange.com/questions/75062/a-simple-question | <p>This is a simple question but it seems to me that both the explanations are acceptable.</p>
<p>Let say the least distance of least distinguished vision is 25 cm.</p>
<p>An object is placed 12.5 cm in front of a plain mirror. Where should my eyes be placed such that I can see the image clearly?</p>
<p>Actually, th... | <p>The <a href="http://en.wikipedia.org/wiki/Plane_mirror" rel="nofollow">virtual image</a> created by the flat mirror is 12.5 cm behind the mirror. Thus, if the <a href="http://en.wikipedia.org/wiki/Lens_%28anatomy%29" rel="nofollow">lens</a> of your eye is making an image of something at a distance 25 cm, you should ... | 706 |
optics | Law of reversibility of light and total internal reflection | https://physics.stackexchange.com/questions/78678/law-of-reversibility-of-light-and-total-internal-reflection | <p>When a light passes from a denser to a rarer medium at critical angle of incidence the light rays graces through the surface of the denser medium.According to the law of reversibility of light same thing should happen when we reverse the direction of light.But, how can that be? How does the light know when to go int... | 707 | |
optics | counting refractive index of a plano convex lens | https://physics.stackexchange.com/questions/81538/counting-refractive-index-of-a-plano-convex-lens | <p>suppose that, there is a plano convex lens and its thickness is 5.00cm. If you watch it straight from the convex side, it seems that its of 4.4 cm. What is the refractive index of this lens?</p>
| <p>Refraction occurs because of the slowing of light in a medium. So the ratio between the actual thickness and perceived thickness is directly related to the ratio of refractive index between that of the lens material and that of air.</p>
| 708 |
optics | conceptual meaning of "virtual image" | https://physics.stackexchange.com/questions/83755/conceptual-meaning-of-virtual-image | <p>I am trying to learn about optics and I am having a hard time understanding the meaning of "real" vs "virtual" image.</p>
<p>My understanding is that for a concave mirror, the image focuses on the same side as the object so it is a real image.</p>
<p>For a convex mirror, the image focuses on the opposite side of t... | <p>The distinction is very simple. A real image is one that the EM radiant energy (rays) actually pass through, so you can put a screen there, and see the image.</p>
<p>A virtual image is an imaginary image. No rays or EM radiation actually passes through it, so you can't see it on a screen placed there, it doesn'... | 709 |
optics | Fluorescence lifetime imaging | https://physics.stackexchange.com/questions/86896/fluorescence-lifetime-imaging | <p>Actually I am not a physics student but I have to give a lecture about Fluorescence lifetime imaging(FLIM). I am thinking of comparing this techniques to another imaging techniques.
Does anyone know what is the best imaging techniques that is comparable to FLIM?
Thank you</p>
<p>Soha</p>
| <p>Although this is kind of trivial, nonetheless I find that many people do not grasp the following points at first glance and struggle under the weight of the misconceptions that follow.</p>
<p>You might try making the analogy between FLIM and doppler shift imaging, such as used in echocardiograms, or with interferom... | 710 |
optics | Propagating higher-order Hermite-Gauss modes using the Complex Beam Parameter? | https://physics.stackexchange.com/questions/92736/propagating-higher-order-hermite-gauss-modes-using-the-complex-beam-parameter | <p>A Gaussian laser beam can be propagated through an optical system (consisting of free space, thin lenses, curved and flat interfaces, etc) by using the "ABCD" <a href="http://en.wikipedia.org/wiki/Ray_transfer_matrix_analysis" rel="nofollow">ray-transfer matrices</a>, and the <a href="http://en.wikipedia.org/wiki/Ra... | <p>The complex beam parameter $\tilde{q}$, otherwise known as the complex radius of curvature, describes the transformation of the fundamental Gaussian mode through an optical system. All of the parameters of the higher order modes can be related to this fundamental mode transformation. </p>
<p>In the case of Gouy p... | 711 |
optics | Could a spatial filter improve a heterodyne signal? | https://physics.stackexchange.com/questions/93520/could-a-spatial-filter-improve-a-heterodyne-signal | <p>Consider two beams of light at slightly difference frequencies that are interfered at a detector. The signal of interest is contained in the phase of the observed signal. As the beams travel around they pass through a variety of optics, which slightly distort the beams' wavefronts. As I understand it, a spatial filt... | <p>It depends somewhat on the specifics of your measurement, but there are some cases in which it will improve your SNR to clean the beam up. This could be accomplished with the use of a spatial filter or a mode cleaner; the mode cleaner will do a better job but will add complexity. </p>
<p>To qualify the first stat... | 712 |
optics | Beam power and electric field after a beam splitter | https://physics.stackexchange.com/questions/93669/beam-power-and-electric-field-after-a-beam-splitter | <p>Consider a beam with power $P_1$ and electric field amplitude $E_{01}$. It is sent through a 50/50 beam splitter that produces beams with power $P_2=P_3=P_1/2$. What are the electric field amplitudes of the split beams, $E_{02}$ and $E_{03}$? </p>
<p>From what I understand, $P=KE_0^2$ where $K$ is a constant. There... | <p>Your error is in how the electric fields are combined by a 50/50 beam splitter. If you have two entry ports $a$ and $b$ with electric field amplitudes $E_a$ and $E_b$, and exit ports $c$ and $d$ with electric field amplitudes $E_c$ and $E_d$, then the correct way to combine them is
$${E_c=\frac1{\sqrt2}(E_a+E_b),\\ ... | 713 |
optics | Reflectance of Titanium as Function of Thin Film Thickness | https://physics.stackexchange.com/questions/33212/reflectance-of-titanium-as-function-of-thin-film-thickness | <p>As far as I know, transmittance equals $e^{-\alpha x}$, where $\alpha$ is absorption coefficient and $x$ is thin film thickness($100-300\,nm$). My team and I have engineered a way to find absorption. Transmittance, T= (Output intensity)/(initial intensity). And, absorption A=(initial intensity-output intensity)/(ini... | <p>Grab a copy of Optical Properties of Thin Solid Films by O. S Heavens. This discusses the transmission and reflection in great detail. There is more info on Google Books <a href="http://books.google.co.uk/books/about/Optical_properties_of_thin_solid_films.html?id=hixRAAAAMAAJ" rel="nofollow">here</a>, but it hasn't ... | 714 |
optics | What is primary reason for a matter to be transparent as Cornea is? | https://physics.stackexchange.com/questions/38979/what-is-primary-reason-for-a-matter-to-be-transparent-as-cornea-is | <p>Is it because its internal structure is Crystalline? I mean by transparency <a href="http://en.wikipedia.org/wiki/Transparency_%28optics%29" rel="nofollow">following</a>.</p>
| <p>No, the <a href="http://en.wikipedia.org/wiki/Cornea" rel="nofollow noreferrer">Cornea</a> is mostly fibrous - not crystalline. </p>
<p>As for the physics of optical transparency - <a href="http://van.physics.illinois.edu/qa/listing.php?id=2046" rel="nofollow noreferrer">here's</a> an elementary introduction</p>
<... | 715 |
optics | Maximum resolution per lens size | https://physics.stackexchange.com/questions/41597/maximum-resolution-per-lens-size | <p>This question is more practical than theoretical, but I am interested in the theoretical considerations as well.</p>
<p>My wife just bought a Samsung S3 phone with a 8 MP image sensor hiding behind a tiny lens. In daylight the pictures come out fine, but it suffers horribly in low-light conditions. Is there a theor... | <p>The resolution is controlled by diffraction at the smallest part of the lens system. The Wikipedia article on <a href="http://en.wikipedia.org/wiki/Angular_resolution" rel="nofollow">angular resolution</a> goes into this in some detail. To quote the headline from this article, for a camera the spatial resolution at ... | 716 |
optics | How big of a lens or parabolic mirror would it take | https://physics.stackexchange.com/questions/44716/how-big-of-a-lens-or-parabolic-mirror-would-it-take | <p>...to heat a piece of steel so its glowing yellow (1100 C)? Assuming you had a cloudless day at a latitude of, say, San Francisco...</p>
<p>Basically I'm wondering if it is possible/feasible to be able to do basic metal working without a traditional forge, just using the power of the sun to heat the metal. So the d... | <p>For steel, the specific heat would be $c_p=0.5 kJ/kg K$, with a density of $
\rho=7000 kg/m^3$. Suppose you want to increase the temperature bij say $\Delta T=1100K$ of a piece of size $V=(15cm)^3$</p>
<p>Then you would need a total energy of.</p>
<p>$$E=\rho c_p V \Delta T$$
Which gives you typically $E=10^7 J$</... | 717 |
optics | Does light shine better through a matt surface or a glossy surface? | https://physics.stackexchange.com/questions/46463/does-light-shine-better-through-a-matt-surface-or-a-glossy-surface | <p>I am currently designing a lighting solution for Phillips as part of my university degree. However I am stuck on a small problem, as stated above. If I was to have a strip of perspex, with the sides matt and the bottom polished, would I achieve more light through the polished surface or the matt surface. And why?? <... | <p>Reading this may help you out: <a href="http://en.wikipedia.org/wiki/Fresnel_equations" rel="nofollow">http://en.wikipedia.org/wiki/Fresnel_equations</a></p>
<p>What you are describing seems to be some sort of light pipe, where you are counting on internal reflection to transport the light along the strip. Whether ... | 718 |
optics | Spectral luminous efficiency as a function of wavelength | https://physics.stackexchange.com/questions/51957/spectral-luminous-efficiency-as-a-function-of-wavelength | <p>I've come across plenty of figures demonstrating the spectral luminous efficiency as a function of wavelength (meaning the humans eye's sensitivity to different wavelengths)
<a href="http://www.yorku.ca/eye/photopik.htm" rel="nofollow">http://www.yorku.ca/eye/photopik.htm</a>
but I've been unable to find the equati... | <p>The equation is approximately:</p>
<blockquote>
<p>V(\lambda)=exp-0.5[(((\lambda-559)/41.9)]^2)</p>
</blockquote>
| 719 |
optics | Erratic light spot in optical projection | https://physics.stackexchange.com/questions/54245/erratic-light-spot-in-optical-projection | <p>I once had an old microscope, that included a projection screen that could be mounted instead the eyepiece. It showed a quite decent palm-sized image. </p>
<p>Now I have a new microscope, and removed the eyepiece to mount a single lens reflex camera. However, the image projected on the ground glass, and also on the... | <p>The type of microscope and illumination scheme are not described. However, in general the microscope produces a real image down inside the tube just below the eyepiece. For attaching a camera, a separate port is sometimes provided such that the camera image sensor can be placed at this real image plane, or at a re... | 720 |
optics | Is there a formula for determining the focal point of a sphere? | https://physics.stackexchange.com/questions/57070/is-there-a-formula-for-determining-the-focal-point-of-a-sphere | <p>I guess this is the same as for cylinders, when light is shone through parallel to the cross-section, but Google-ing this only turns up lenses like the ones used in glasses.</p>
<p>I'm looking for something like what's described in this article: <a href="http://spie.org/x34513.xml" rel="nofollow">http://spie.org/x3... | <p>At your request. Here's <a href="http://mysite.du.edu/~jcalvert/astro/heilig.htm" rel="nofollow">somebody</a> working it out for you.</p>
| 721 |
optics | Circular polarisation | https://physics.stackexchange.com/questions/57123/circular-polarisation | <p>If we have a planar and harmonic EM wave, with $B$ field:</p>
<p>$$B=A\left(\begin{array}{c}
1\\
i\\0
\end{array}
\right)e^{-i(\omega t-\vec k\cdot\vec r)}$$</p>
<p>and with it's corresponding $E$ field. This is a circularly polarised wave, but that field does not have 0 divergence, the three components of it, whe... | <p>$\vec{E}$ has not different phase, but different polarisation :
$\vec{B} = \vec{n}\times\vec{E}$</p>
<p>Yes, this solution cannot be a solution of Maxwell's equations for all $\vec{k}$, cause $\nabla{ \vec{E}} =0$ for $\vec{E} = \vec{E_0} e^{-i(\omega t - \vec{k}\vec{r})} $ implies $\vec{k} \vec{E_0} = 0$, so elect... | 722 |
optics | What is the effect of refractive index of an object for imaging? | https://physics.stackexchange.com/questions/56114/what-is-the-effect-of-refractive-index-of-an-object-for-imaging | <p>My Question is as follows.</p>
<p>What is the effect of refractive index of an object for imaging (Photographs by high speed camera) on its size and shape information incurred from image?</p>
<p>Lets say ,</p>
<p>I keep the camera focal length, aperture, distance between camera & object, light intensity of t... | <p>A while back I did an experiment imaging oil droplets in water, where we used oils of differing refractive index. Is this the sort of thing you're interested in?</p>
<p>If so, assuming your camera is in focus it will accurately record the size of the oil droplet so varying the refractive index will not cause the <e... | 723 |
optics | Fraunhofer diffraction simulation for a hexagonal aperture, what are the typical units? | https://physics.stackexchange.com/questions/60070/fraunhofer-diffraction-simulation-for-a-hexagonal-aperture-what-are-the-typical | <p><a href="https://physics.stackexchange.com/a/9910/22775">Kostya answered a question</a> that was asking what the diffraction pattern looks like for a hexagonal aperture in front of a lens. He lists an equation which was derived using a Heaviside function to describe the shape of the aperture.</p>
<p>I was wonderin... | <p>What I've calculated is just a Fourier transform of the aperture $h(x,y)$:</p>
<p>$$f(\omega_x,\omega_y)=\int dx\, dy\, h(x,y)e^{-i(\omega_xx+\omega_yy)}$$</p>
<p>(And I was plotting $|f|^2$ as a function of $\omega_{x,y}$ each changing from -100 to 100.)<br>
Already here one can see that $\omega_{x,y}$ both have ... | 724 |
optics | How do you calculate heat flux (Kw/m2) at the focal point of a mirror? | https://physics.stackexchange.com/questions/60541/how-do-you-calculate-heat-flux-kw-m2-at-the-focal-point-of-a-mirror | <p>can anyone help me to determine the heat flux (Kw/m2) on a focal point of a parabolic dish having a diameter of 1.5 meter and a focal length 60 cm ???
please awaiting your soonest reply for my senior project :(
Regards</p>
| <p>In any practical application, the flux measured is the <em>average</em> over the area of the measuring apparatus.</p>
<p>In the limit of a perfect dish, an infinitely far away source, and no diffraction, then the flux would be infinite at a single point and zero everywhere else in that plane. But all of these condi... | 725 |
optics | How does Telescope lens work? | https://physics.stackexchange.com/questions/8693/how-does-telescope-lens-work | <p>1.How does a Telescope work?
2.What factors increase the magnification of the lens?</p>
| <p>It's not quite clear what you mean by "telescope lens" - do you mean the system of lenses that make up a telescope? If so, there are two basic types. The actual lenses in your telescope are probably more complicated and correct for all kinds of <a href="http://en.wikipedia.org/wiki/Spherical_aberration" rel="nofollo... | 726 |
optics | Optical distortions and focus losses calculation | https://physics.stackexchange.com/questions/11875/optical-distortions-and-focus-losses-calculation | <p>I'm working with a megapixel camera and lens that needs to be focused for an OCR application. In order to measure the focus quality during the set-up, I've built a tool that gives the contrast value between two pixels. In very simply words, more the contrast is high more the focus is good...
Due to optical distortio... | <p>You cannot figure that via pure math. It 100% depend of specific lens design you have - you could have 0 difference, you could have sphere-like focal plane, you could have anything.</p>
<p>So your best bet is to measure focal plane differences across the frame, and interpolate.</p>
| 727 |
optics | Impact of covering glass on lens performance | https://physics.stackexchange.com/questions/11978/impact-of-covering-glass-on-lens-performance | <p>I've seen microscope lenses optimized for 0.17mm covering glass. I don't see what needs to be optimized here? As glass does not touch the lens (as in case of oil/water immersion) - it should just affect focal distance without introducing any aberrations. </p>
<p>Is that correct, or covering glass will cause aberrat... | <p>Any time you know there will be something in your optical system, it is generally good practice to include it in your model during the design process. Of course, in many applications these things will not make a difference. The image quality of your point-and-shoot camera will not become unacceptable if somebody cho... | 728 |
optics | Magnification multiplication using telescope arrays? | https://physics.stackexchange.com/questions/12016/magnification-multiplication-using-telescope-arrays | <p>If we have an array of telescopes attached one after another, would the resultant magnification be multiplied?Also would such a contraption be feasible to make telescopes with amazing magnification?</p>
| <p>If you head down to your local telescope shop and check out their inventory, you might see two telecopes. One is a refractive telescope with a 2 inch aperture, and it has its magnification listed as 1 million. Another is a reflective telescope with a 6 inch aperture and a magnification of 200. Which will allow you... | 729 |
optics | Projecting image without manual focussing | https://physics.stackexchange.com/questions/12563/projecting-image-without-manual-focussing | <p>I was wondering if it was possible to project a magnified image on a wall without the need of focusing, so just by dimensioning the lenses right.</p>
<p>I know I have to use the principal of Maxwellian View for the illumination of the slide. However, there are a lot of parameters left and I can design a system that... | <blockquote>
<p>I was wondering if it was possible to project a magnified image on a
wall without the need of focusing, so just by dimensioning the lenses
right.</p>
</blockquote>
<p>Of course You can!</p>
<p>The real problem is that You do not know the exact position of the slide
in its holder.
Second proble... | 730 |
optics | Diffraction pattern threshhold | https://physics.stackexchange.com/questions/12359/diffraction-pattern-threshhold | <p>What is the characteristic bump height of periodic grating below which diffraction effect cease to exist (let assume a threshold of peaks to valleys intensity of 20% as the minimum detectable by human eye). Is it significantly less than lambda?</p>
| <p>Assume sinusoidal grate -- <code>sin(x)</code> is the simplest possible periodic function. Direct axis <code>x</code> horizontally, and <code>y</code> vertically, and lets calculate diffraction at the point <code>(x,y)</code>. According to Fraunhofer diffraction we must first calculate distance from the observation ... | 731 |
optics | Refractive index liquids: Why hard to buy? | https://physics.stackexchange.com/questions/12466/refractive-index-liquids-why-hard-to-buy | <p>Does anyone know the refractive index suppliers? I've found Cargille Labs (which customer service is terrible so far but the liquids may actually be OK), but nothing else comparable. I'd like to have a set of liquids with the refractive index in the range of 1.3...1.4. Are they so hard to produce that almost nobody ... | 732 | |
optics | Is the Sun-set and the Sun-rise Symmetrical for the Observer? | https://physics.stackexchange.com/questions/15324/is-the-sun-set-and-the-sun-rise-symmetrical-for-the-observer | <p>Is there the effect of sun rising and sun setting, in terms of Rayleigh scattering and visual spectrum and other factors completely similar and symmetric? I mean can one recognise them from a picture taken from the sky?</p>
| <p>The average air temperature is always lower at sunrise, which changes the atmospheric refraction infinitesimally. On the moon, you would only have the tiny difference from the doppler shift due to your motion relative to the sun, so that sunrise would be a teeny-weeny bit bluer than sunset.</p>
| 733 |
optics | Which device amplifies the optical signal in fiber optics? | https://physics.stackexchange.com/questions/15388/which-device-amplifies-the-optical-signal-in-fiber-optics | <p>My teacher ask me one question. How the optical signal or information was transfered in fiber optics communication?</p>
<p>Then i explained it and use the word optical amplifier then teacher ask me what is optical amplifier i said which amplifies optical signal then again which device amplifies the optical signal i... | <p>An optical amplifier works just like a laser, but with a few small differences. In a laser, light is created, usually due to spontaneous emission from the gain medium. Light then circulates in an optical cavity while being further amplified in the gain medium. A single photon can traverse the laser cavity many milli... | 734 |
optics | What sets the resolution on analog film? | https://physics.stackexchange.com/questions/17245/what-sets-the-resolution-on-analog-film | <p>When taking a picture with old fashioned film what sets the resolution of the picture? Is it the wavelength, or the chemical makeup of the film?</p>
| <p>Both the diffraction limit and the grain size could affect the resolution limit of analog pictures. Let's see how they compare.</p>
<p><strong>Diffraction limit</strong>
The Abbe diffraction limit states that the size of the spot is $d=\lambda f\#$. The $f$-number will depend widely for different cameras and illumi... | 735 |
optics | Does a perfect mirror behave the same as a blackbody radiator? | https://physics.stackexchange.com/questions/19668/does-a-perfect-mirror-behave-the-same-as-a-blackbody-radiator | <p>If I put a perfect mirror(i.e. reflects with no attenuation) next to a blackbody radiator its spectra should be the same as the blackbody radiator.</p>
<p>Looking only at the spectra - is there any difference between a blackbody radiator and a perfect mirror? </p>
<p>For instance, suppose the mirror is acceleratin... | <p>A mirror at rest (or moving at constant velocity) emits no thermal radiation whatsoever.</p>
<p>Detailed balance, i.e. 2nd law of thermodynamics, requires a relationship between absorbing incoming radiation and turning it into heat, versus emitting thermal radiation. A perfect mirror at rest does not absorb any inc... | 736 |
optics | How it's possible to enhance the depth effect of 3d pictures without increasing the cameras distance? | https://physics.stackexchange.com/questions/20088/how-its-possible-to-enhance-the-depth-effect-of-3d-pictures-without-increasing | <p>I always thought that for a 3d picture, which is in fact 2 pictures that are displayed one for each eye, the more far the cameras are, the more "depth" you will see. And it's a fact i think.</p>
<p>So, for example, if you take the picture of a house and the cameras distance is let's say, 10m, you'll have the impres... | <p>For the reasons that you already mentioned in the question, it would not be possible to modify stereoscopic depth without adding artifacts.</p>
<p>So instead I would argue if the depth is actually increased. It probably isn't.</p>
<p>We have gotten used to watching monoscopic (regular) photographs with both our ey... | 737 |
optics | How could I translate a field of view value into a magnification value? | https://physics.stackexchange.com/questions/26046/how-could-i-translate-a-field-of-view-value-into-a-magnification-value | <p>When I zoom in with <a href="http://www.stellarium.org/" rel="nofollow">Stellarium</a>, it indicates a field of view (FOV) value in degrees, but most binoculars and telescopes are advertised with value like "nX magnification power."</p>
<p>How could I translate this value so I get an idea of what I will see with a ... | <p>Different telescope and binocular eyepieces have different fields of view, so that there is no direct relationship between magnification and field of view.</p>
<p>Eyepieces range in apparent field of view from 30° to 110°, typically being in the range of 50° to 70°. For any given eyepiece, you can calculate the act... | 738 |
optics | How much detail can telescopes actually provide? | https://physics.stackexchange.com/questions/26172/how-much-detail-can-telescopes-actually-provide | <p>For example, could the numbers / letters on a postage stamp in a randomly specified location be clearly visible from space.</p>
<p>This is to settle a discussion with a friend that piqued my curiosity. </p>
| <p>Two major issues here. Well, maybe three...</p>
<ul>
<li>Optical limits of the instrument. Think <a href="http://en.wikipedia.org/wiki/Angular_resolution">Rayleigh Criterion</a>, but beware of the existence of interferometric methods (hard to do in the optical for now, but...). It's going to take a <em>big</em> len... | 739 |
optics | Is periscope window mathematically possible? | https://physics.stackexchange.com/questions/413909/is-periscope-window-mathematically-possible | <p>I was always wondering, why don't we have periscope windows?
What I imagine is a "light intake" on a roof, from which the light is concentrated into a straight long <strong>narrow</strong> tube that takes it to an underground flat where the light is dispersed into a fake window.</p>
<p>Is such design mathematically... | <p>Depends on how narrow this tube is. Without moving optics that can track the sun, the tube must be as large as the collection area, and no kinds of tricks with mirrors or lenses can make it better. If sun-tracking optics are allowed then you can do much better, provided it's not cloudy.</p>
<p>Let's start with a pr... | 740 |
optics | Is a converging gaussian beam just another gaussian beam with a much larger Rayleigh length? | https://physics.stackexchange.com/questions/414673/is-a-converging-gaussian-beam-just-another-gaussian-beam-with-a-much-larger-rayl | <p>This link seems to imply it, but I'm confused. Also, I don't intuitively see how the general shape of the gaussian remains the same. I'd expect it to be some kind of surposition between a normal gaussian and converging lines, like a $e^{-x} * sin$ function. <a href="https://www.ophiropt.com/blog/laser-measurement/fo... | <p>Yes, all (theoretical) Gaussian beams are the same, no matter whether they are collimated or converging. There is always a waist (though it may not be in the portion of the beam that actually exists.)</p>
<p>A sharply converging Gaussian beam has a short Rayleigh length.</p>
<p>There is no such thing as a perfectl... | 741 |
optics | how does PBS(polarized beam splitter) work? | https://physics.stackexchange.com/questions/415758/how-does-pbspolarized-beam-splitter-work | <p>I know that beam splitter work with evanescent wave, and by adjusting the thickness between the two prism you can control the R,T to be 50%,50%.
But how does polarized beam splitters work?</p>
| <p>There are several different types of polarizing beam splitters. For example, if we have incident unpolarized light, a stack of plates tilted at the brewster angle would do the trick. The main pillar of this theory is that s-polarized and p-polarized light have different reflectivities for different incident angles.T... | 742 |
optics | Evaluation of Fresnel coefficient for $\theta_{i}>\theta_{cr}$ | https://physics.stackexchange.com/questions/450992/evaluation-of-fresnel-coefficient-for-theta-i-theta-cr | <p>For a TE wave the Fresnel coefficient <span class="math-container">$r$</span> is:
<span class="math-container">$$r=\frac{\cos(\theta_{i})-\sqrt{n^2-\sin^2(\theta_{i})}}{\cos(\theta_{i})+\sqrt{n^2-\sin^2(\theta_{i})}}$$</span>
if <span class="math-container">$\theta_{i}>\theta_{cr} \rightarrow (n^2-\sin^2(\theta_{... | 743 | |
optics | How do Raman pulses, transitions and diffraction processes work? | https://physics.stackexchange.com/questions/508675/how-do-raman-pulses-transitions-and-diffraction-processes-work | <p>I want to know how Raman pulses work. Also, can someone explain to me Raman transitions and Raman diffraction processes?</p>
<p>Additionally, how does phase get accumulated in the free evolution of any hyper-fine states in an atom? </p>
| <p>Well the conventional lasers rely on electronic transitions for amplification of light. The Raman lasers on the other hand make use of Raman scattering for light amplification. Raman lasers are optically pumped systems. This pumping does not produce an inversion of our photon group as in electronically stimulated la... | 744 |
optics | How to derive equation (upper bound for the period to-wavelength, grating) | https://physics.stackexchange.com/questions/513667/how-to-derive-equation-upper-bound-for-the-period-to-wavelength-grating | <p>I am currently reading the paper entitled "Antireflection behavior of silicon subwavelength periodic structures for visible light" [P. Lalanne & G Michael Morris, <a href="https://doi.org/10.1088/0957-4484/8/2/002" rel="nofollow noreferrer"><em>Nanotechnology</em> <strong>8</strong>, 53 (1997)</a>].</p>
<p>On th... | 745 | |
optics | What causes a transmissive diffraction grating to be more effective than a reflective one? | https://physics.stackexchange.com/questions/607498/what-causes-a-transmissive-diffraction-grating-to-be-more-effective-than-a-refle | <p>I was curious as to what would make a transmissive grating more effective than a reflective one. I have been searching but am having trouble finding an answer.</p>
<p>In literature, some semitransparent biological materials are iridescent under (oblique) transmitted light. However, the same materials, under epi illu... | <p>The efficiency of a diffraction grating, whether transmissive or reflective, depends on several factors. One of them is the shape and depth of a grating. The depth of the grating controls how much energy gets sent to each diffracted order. The ideal depth for a transmissive grating depends on the refractive index ... | 746 |
optics | Does no airy disk/pattern mean that a converging beam of light is not at its focal plane? | https://physics.stackexchange.com/questions/415042/does-no-airy-disk-pattern-mean-that-a-converging-beam-of-light-is-not-at-its-foc | <p>From wikipedia: "In optics, the Airy disk (or Airy disc) and Airy pattern are descriptions of the best focused spot of light that a perfect lens with a circular aperture can make, limited by the diffraction of light."</p>
<p>So, is this saying that if I have a camera looking at a converging beam laser, that I am go... | 747 | |
optics | Focal length problem | https://physics.stackexchange.com/questions/201776/focal-length-problem | <p>Let we have an biconvex lens with equal radii, that means the two radii of curvature are equal. We know that from lens equation, </p>
<p><a href="https://i.sstatic.net/jxvqA.gif" rel="nofollow noreferrer"><img src="https://i.sstatic.net/jxvqA.gif" alt="enter image description here"></a></p>
<p>For biconvex lens, $... | <p>Any formula in physics comes with a set of definitions of what each variable in the equation represents, and how to interpret positive or negative values. This is particularly rue in the case of lens and mirror formulae. In each case, a different form of the equation, with a different set of definitions, will give... | 748 |
optics | Difference in the grating spectrum with different sources | https://physics.stackexchange.com/questions/206214/difference-in-the-grating-spectrum-with-different-sources | <p>If we use a slit source [of monochromatic light] in a diffraction grating setup we obtain parallel bands on screen. If instead of slit we use a point source we don't have such bands. Can someone please explain why and how does this happen?
<a href="https://i.sstatic.net/lp0sy.jpg" rel="nofollow noreferrer"><img src... | <p>The lenses project the image of the light source on the screen. The grating does not affect the propagation in the z-direction, so in one case you have lines that are offset in the x-direction depending on diffraction order and wavelength in the other case you have points that are offset.</p>
<p>So the grating does... | 749 |
optics | Incident angle and refracted angle | https://physics.stackexchange.com/questions/220606/incident-angle-and-refracted-angle | <blockquote>
<p><a href="https://i.sstatic.net/8EmUm.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/8EmUm.jpg" alt="enter image description here"></a></p>
</blockquote>
<p>I came across this picture while studying about Huygens' principle and Laws of Refraction.In my book I saw that it is mentioned $... | <p>I agree that's confusing, and that $\theta_2$ is just plain wrong. I've always seen it explained with the normal perpendicular to the surface, just like you say, and exactly as drawn in <a href="https://en.wikipedia.org/wiki/Snell%27s_law" rel="nofollow">https://en.wikipedia.org/wiki/Snell%27s_law</a> But note that... | 750 |
optics | 3D glasses: how do we tell whether a doubly-rendered image is closer or farther than the screen? | https://physics.stackexchange.com/questions/228987/3d-glasses-how-do-we-tell-whether-a-doubly-rendered-image-is-closer-or-farther | <p>This is a followup to this question:
<a href="https://physics.stackexchange.com/questions/228887/3d-glasses-giving-the-opposite-effect-to-that-expected">3D glasses giving the opposite effect to that expected</a></p>
<p>The current top answer explains that objects perceived as beyond the plane of the screen, as well... | <p>As you can see from the sketch you posted, there is exactly one point where the corresponding rays traveling to each eye cross (marked by the solid dots). Our brain sees this light as if it emerged out of this single point (while in fact it came from two spots on the screen).</p>
<p>The brain processes the images p... | 751 |
optics | Why is there "ringing" at the violet end of a rainbow but not the red end? | https://physics.stackexchange.com/questions/230705/why-is-there-ringing-at-the-violet-end-of-a-rainbow-but-not-the-red-end | <p>I've recently noticed that if you look closely at the violet end of a rainbow, you can see a sort of "ringing" effect where there are alternating bands of color and lack of color. You can apparently photograph this:</p>
<p><a href="https://i.sstatic.net/Fa5au.jpg" rel="nofollow noreferrer"><img src="https://i.sstat... | <p>On rainbow formation: <a href="https://en.wikipedia.org/wiki/Rainbow#Supernumerary_rainbow" rel="nofollow noreferrer">https://en.wikipedia.org/wiki/Rainbow#Supernumerary_rainbow</a> . See a bit more about supernumeraries here <a href="http://www.atoptics.co.uk/rainbows/supers.htm" rel="nofollow noreferrer">http://ww... | 752 |
optics | Diffraction pattern in the image plane? | https://physics.stackexchange.com/questions/237147/diffraction-pattern-in-the-image-plane | <p>Consider the setup below:
<a href="https://i.sstatic.net/z4GxS.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/z4GxS.png" alt="enter image description here"></a></p>
<p>In all cases the relationship between $u_o(x_o)$ and $u_f(x_f)$ is given by a Fourier transform. My question is, when is the same tr... | <p>Strictly speaking, it's not true that in all cases the relationship is an exact Fourier Transform. Since we're dealing with electric-fields, unless the object is exactly one focal length away from the lens all other cases will have a quadratic factor that needs to be dealt with, unless you're interested in the pure... | 753 |
optics | Why is the wavelength of light proportional to the minimum angle of resolution? | https://physics.stackexchange.com/questions/255421/why-is-the-wavelength-of-light-proportional-to-the-minimum-angle-of-resolution | <p>E.g. why does the minimum angle of resolution increase as wavelength increases?</p>
<p><a href="https://i.sstatic.net/yebCM.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/yebCM.jpg" alt="Resolution and the Rayleigh Criterion"></a></p>
| <p>I like to look at it the other way around: the minimum resolving angle depends on your wavelength. That's why people use X-rays to look at crystal structures for instance. In imaging, where one typically uses spherical apertures, the best focus that can be obtained is not a single spot but a so-called Airy pattern. ... | 754 |
optics | Why don't windows and mirrors cancel light? | https://physics.stackexchange.com/questions/264465/why-dont-windows-and-mirrors-cancel-light | <p><a href="https://i.sstatic.net/I28Gl.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/I28Gl.png" alt="enter image description here"></a>So I understand that when light goes from a material of low index to a material of higher index it picks up a phase change of 180. Most glass has an index of around 1.... | <p>What you have not taken account of is that the light wave reflected is travelling in the opposite direction. The incoming and outgoing waves may interfere with each other, but they will not completely cancel each other out - in fact a standing wave may be formed as described below.</p>
<p>Now - the way an antiflect... | 755 |
optics | A confusion about single slit diffraction | https://physics.stackexchange.com/questions/303688/a-confusion-about-single-slit-diffraction | <p>I am studying wave optics at home. Yesterday I came across a diagram depicting single slit diffraction experiment of light, where they placed a convex lens. I could not understand the purpose of this convex lens.<a href="https://i.sstatic.net/WUH8r.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/WUH8r... | 756 | |
optics | 3D glasses which bend light about 5-10 degrees - how do they work? | https://physics.stackexchange.com/questions/596903/3d-glasses-which-bend-light-about-5-10-degrees-how-do-they-work | <p>A child's jigsaw puzzle came with two pairs of cheap cardboard-framed 3D glasses.</p>
<p>The glasses had thin plastic film in them, as lenses.</p>
<p>These thin flat plastic lenses bend about 99% of visible light by around 5-10 degrees. You can see a very faint image of the unbent scene.</p>
<p>This produces a weak... | 757 | |
optics | Geometrical paraxial optics | https://physics.stackexchange.com/questions/597607/geometrical-paraxial-optics | <p>Why is geometrical optics treated in 2d? I actually never thought about it and calculated all the problems straightforward with the ABCD matrices. And then this question came to my mind for which I have no answer so far.</p>
| <p>Usually optical systems are axially symmetric, so that you only need 2 d to understand the paths of all the rays traversing the system.</p>
| 758 |
optics | How to choose the right focal length lens for my photodetector? | https://physics.stackexchange.com/questions/606315/how-to-choose-the-right-focal-length-lens-for-my-photodetector | <p>I wanted to know how to choose the right focal length lens for my silicon carbide photodetector which has a peak response of 315nm and an active area of 25mm^2 such that I can mount that lens on my photodetector to reject any ambient light and allow only UV light to pass through it. Kindly share your thoughts.</p>
| 759 | |
optics | Is there a relationship between thickness of matter and luminance? | https://physics.stackexchange.com/questions/613530/is-there-a-relationship-between-thickness-of-matter-and-luminance | <p>I'm searching for a relationship between thickness of matter and luminance.</p>
<p>I'm a tribologist and I'm doing friction and wear experiments. During these experiments I'm illuminating the surface and capturing images during the whole test. The incoming light is a diffused light generated by a lighting dome. I'm ... | 760 | |
optics | Why does light refract if photons are not bound by an axle? | https://physics.stackexchange.com/questions/2169/why-does-light-refract-if-photons-are-not-bound-by-an-axle | <p>In the classic metaphor, a light beam bends for the same reason that a wagon getting one wheel stuck in the sand does...the wheels travel at uneven speeds, and the wheel on the smoother surface travels faster.</p>
<p>But the key to the wagon scenario is the axle - if the two wheels were not bound, the faster wheel ... | <p>First important point is that light always travels in a straight lines in an environment of constant index of refraction:</p>
<p><img src="https://i.sstatic.net/eejRR.gif" alt="alt text"></p>
<p>What creates the dispersion is the fact that the index of refraction depends on the frequency of the light $n = n(f)$. T... | 761 |
optics | Will watering tea down make it clearer? | https://physics.stackexchange.com/questions/4709/will-watering-tea-down-make-it-clearer | <p>If I poured water into my tea, would I see more or less of the bottom of the tea-cup?</p>
<p>Intuitively, there would be as many particles blocking as many photons, and so I'd see the bottom just as clearly as before.</p>
| <p>There is some misconception in Tims question already: </p>
<blockquote>
<p>as many particles blocking as many photons, and so I'd see the bottom just as clearly as before</p>
</blockquote>
<p>Blocking of photons will not impair clarity at all! </p>
<p>One has to distinguish absorption and scattering! Tea is a ... | 762 |
optics | Will the size of the pinhole affect the size of the image produced? | https://physics.stackexchange.com/questions/582174/will-the-size-of-the-pinhole-affect-the-size-of-the-image-produced | <p>If we have a larger pinhole, would it produce a larger image? <br />
I know the size of the opening will affect the brightness and sharpness of the image, but what about its size? If you think about it, a wider opening will make the light rays more spread out and therefore consequently produce a bigger (and also blu... | <p>A larger pinhole in a pinhole camera does not make the image larger ; it simply makes each "point" in the image blurrier. A way to think about it is to consider the image to be the superposition of a large number of essentually identical images, each produced by a different sub-pinhole in the large pinhol... | 763 |
optics | Why does incident ray, refracted ray and normal lie in the same plane? (looking for physical reasons) | https://physics.stackexchange.com/questions/585403/why-does-incident-ray-refracted-ray-and-normal-lie-in-the-same-plane-looking | <p>If we have a ray striking a plane then the unit vector in direction of the incident ray can be thought of as rotating in a plane that contains the normal to interface and the part of the unit vector along the plane of the interface.</p>
<p>However, I can not understand why this unit vector is not rotated around line... | <p>Why ... because of the equations. That is the best answer there can be, IMHO. Maths is the pure logic</p>
<p>One short-hand I would use it to point out that Maxwell's equations are invariant under rotations, i.e. Maxwell's equations have no preferred direction. In the problem with refraction you have:</p>
<p>(1) Pla... | 764 |
optics | Is there a limit to demagnification of an image as there is for magnification? | https://physics.stackexchange.com/questions/587416/is-there-a-limit-to-demagnification-of-an-image-as-there-is-for-magnification | <p>In making wafers for chips, when using masks and demagnifying to a smaller size, is there any limit to demagnification? For light, a microscope’s numerical aperture and wavelength limitation prevents the level of magnification from becoming higher than a certain level.</p>
| <p>The optical resolution limit is <span class="math-container">$p = 0.5 \lambda / NA$</span> for off-axis illumination. The numerical aperture <span class="math-container">$NA=n \sin \theta$</span> cannot exceed the refractive index <span class="math-container">$n$</span> of the medium (vacuum or sometimes water) belo... | 765 |
optics | Bulb inside the prism | https://physics.stackexchange.com/questions/591428/bulb-inside-the-prism | <p>What if a source of white light is within the prism itself. Let's say it emits a thin beam of white light. Now the speed of different wavelengths is different but it is not being refracted at a surface (atleast until it emerges from the other side), so what will happen to it? Will it stay together as white light onl... | <p>Put simply: the white light, assuming it hits the face of the prism at an angle other than perpendicular, will be spread over angles of exit by color (so long as the prism glass has a nonuniform index of refraction).<br />
You are correct that there will be some phase lag inside the prism, so if you were to generate... | 766 |
optics | A lens with a variable refractive index | https://physics.stackexchange.com/questions/173808/a-lens-with-a-variable-refractive-index | <p>(60th Polish Olympiad in Physics)</p>
<blockquote>
<p>A planoconvex lens of radius of curvature <span class="math-container">$R$</span> and thickness <span class="math-container">$d$</span> (on the optical axis) is made of a material, whose refractive index changes with the distance from the axis according to the fo... | 767 | |
optics | Helical wavefronts of vortex beams | https://physics.stackexchange.com/questions/568765/helical-wavefronts-of-vortex-beams | <p>Vortex beams are characterized by an azimuthal angle phase dependence, basically <span class="math-container">$e^{i l\phi}$</span>. Why is this azimuthal angle phase dependence crucial and will I get a helix if I were to plot the surface of constant phase for Laguerre Gaussian beams?</p>
<p>NB: I have edited the que... | <p>If the wave propagates in the <span class="math-container">$z$</span> direction and <span class="math-container">$\Phi(z,r, \phi,t)$</span> is the phase of the wave
<span class="math-container">$$
A(r)e^{i\Phi(z,r, \phi,t)}=
A(r)e^{ikz -i\omega t+il\phi},
$$</span>
then the surfaces of constant <span class="math-co... | 768 |
optics | Why rainbow doesn't happen in each drop independently? | https://physics.stackexchange.com/questions/244199/why-rainbow-doesnt-happen-in-each-drop-independently | <p>When rainbow happens,we see the rainbow as a whole.</p>
<p>When the light enter each drop,the chromatic dispersion should happen in each drop independently and we should see multiple small rainbows.</p>
<p>So why do we see it as a big one?</p>
| <p>What you see when you're viewing a rainbow at any particular point is the light from the sun reflecting off droplets at that particular point to hit your eye. The angle from which the light hits those droplets to get to your eye is always the same, hence all the droplets in that vicinity show one single color.</p>
... | 769 |
optics | rare occurence of diffraction in light | https://physics.stackexchange.com/questions/246335/rare-occurence-of-diffraction-in-light | <p>My question is that how the diffraction is not a common phenomenon of light.Here the lunar eclispe also is on the same basis but the diffraction is only a feature of sound .how?</p>
| <p>Noticeable diffraction occurs when the wavelength is similar in size to the obstacle in the path of the waves. Sound waves are in the order of metres so we observe diffraction of sound fairly routinely. Since the wavelength of light is so much smaller (and particularly tiny compared to the moon) we rarely see diff... | 770 |
optics | Spherical aberration in concave mirrors | https://physics.stackexchange.com/questions/249384/spherical-aberration-in-concave-mirrors | <p>I saw this posted on the forum with an answer:
<a href="https://physics.stackexchange.com/questions/209716/cause-of-spherical-aberrations">Cause of Spherical Aberrations</a></p>
<p>However, the answer helps explain aberration in lenses. Why is there spherical aberration in concave mirrors?</p>
<p>Thanks,
-Prasad</... | <p>It just geometry. If you want all incident rays parallel to the principal axis to reflect through a single point the mirror needs to parabolic in shape. For a focal length <em>f</em> the equation of the parabola (opening upwards) would be $4fy=x^{2}$.</p>
<p>A spherical mirror will have approximately the same sha... | 771 |
optics | How does total internal reflection cause sparkling of diamonds? | https://physics.stackexchange.com/questions/249767/how-does-total-internal-reflection-cause-sparkling-of-diamonds | <p>How does total internal reflection cause sparkling of diamonds? What is the problem with ordinary glass?</p>
| <ol>
<li>The <em>index of refraction</em> for diamond is much larger than for ordinary glass which means the critical angle in air is much smaller. More rays inside the diamond will experience total internal reflection than would in glass.</li>
<li>The <em>dispersion</em> value for diamond is much higher than for glas... | 772 |
optics | Michelson interferometer | https://physics.stackexchange.com/questions/228678/michelson-interferometer | <p>I'm reading about an experiment done with this piece of equipment. The aim is to measure the thickness of a piece of plastic. They use white light, so the central fringe in the interference pattern, corresponding to equal path lengths in the two beams can be used as a reference. Why does that work?? I don't understa... | <p>I'm not sure that I understand your set up, but it appears to refer to <a href="https://en.wikipedia.org/wiki/Optical_coherence_tomography" rel="nofollow">Optical Coherence Tomography</a>. There are various ways to do it, but in the simplest incarnation, light with a short coherence length is used, and one "mirror... | 773 |
optics | Why we see more diverging light rays than converging light rays? | https://physics.stackexchange.com/questions/148154/why-we-see-more-diverging-light-rays-than-converging-light-rays | <p>While the apparent fact that there's more diverging light rays than convergings ones seems to be intuitive, mathematically I can't find a reason to be so.</p>
<p>More specifically, given a vector field of light rays $\overrightarrow{v}\left(x,y,z,t\right)$, we want to find its overall divergence, i.e integrating it... | <p>Yes, you are missing the second law of thermodynamics. It is related to entropy, the arrow of time, etc. (search wikipedia for great details). Basically, your scenario of equal diverging and converging rays will only happen at thermodynamic equilibrium. The laws of physics are invariant to time reversal, but partic... | 774 |
optics | High power beam splitting | https://physics.stackexchange.com/questions/86398/high-power-beam-splitting | <p>I'm trying to split a high power laser (1064nm, 20W, beam diameter @ 1/e^2 intensity: 3.2mm) into two beams and couple them after some additional optics into two SMF's (single mode fiber). So far I tried a PBS (polarizing beam splitter) cube and a NPBS (non polarizing beam splitter) cube. I can split the beam but th... | <p>Well do we know if the high powered laser is itself polarized, or not?? Using any ordinary 50-50 beam splitter cube at 20 Watts, is likely to create problems with damage to the polarizing splitter medium of such a cube.</p>
<p>It is possible to make beam splitter cubes, specially at well controlled wavelengths, us... | 775 |
optics | Mirrors/optics and physical adaptation of the eye | https://physics.stackexchange.com/questions/675951/mirrors-optics-and-physical-adaptation-of-the-eye | <p>Is it possible to use a clever combination of lenses and mirrors placed between your eye and a screen 1m away from you to make the eye react to the screen as if it were 20m away from you?</p>
<p>Note that I'm not asking whether it's possible to make the light rays travel a total distance of 20m, but whether the eyes... | <p>You mean aside from using lots of mirrors so that the light actually travels 20 m before it hits your eye?</p>
<p>Yes you can do this, from a lens point of view you just want to change the divergence of the rays from a single point. If it is 1 m away they will be more divergent and require more power to focus by you... | 776 |
optics | Do the Fresnel equations of reflection apply to monochromatic light? | https://physics.stackexchange.com/questions/498946/do-the-fresnel-equations-of-reflection-apply-to-monochromatic-light | <p>I have a monochromatic light source (wavelength ~ 420 nm), which will be incident on the interface of two different media. Could someone please explain if the Fresnel equations applies with monochromatic light when estimating the reflectance and transmittance?</p>
<p>Fresnel equation:</p>
<p><span class="math-cont... | <p>Monochromatic simply means that the light is of constant frequency. The frequency only affects the value of the refractive index for dispersive media. It has no affect on the formulae for the Fresnel coefficients. If your monochromatic light is unpolarized, then you need to average over all possible polarizations to... | 777 |
optics | Optical Tweezers: Trap Stiffness for Calculating External Force | https://physics.stackexchange.com/questions/679449/optical-tweezers-trap-stiffness-for-calculating-external-force | <p>I've been reading <a href="https://www.osapublishing.org/aop/fulltext.cfm?uri=aop-13-1-74&id=448989" rel="nofollow noreferrer">this article</a> about calibrating optical tweezers (finding the trap stiffness <span class="math-container">$\kappa$</span>). Around the end of section 2.2 it says</p>
<blockquote>
<p>O... | <p>Once you have your optical trap calibrated and stable, you want to do something useful with it. Maybe you wish to measure flow-induced drag; this is an external force. Maybe you wish to measure the stiffness of a molecule that you'll stretch between the particle and a rigid substrate; this is an external force. Mayb... | 778 |
optics | How would one characterize intensity of diffuse scattering as a function of roughness | https://physics.stackexchange.com/questions/208251/how-would-one-characterize-intensity-of-diffuse-scattering-as-a-function-of-roug | <p>How would one even characterize roughness of a material experimentally using statistical analysis or by a set of equations
And how would I relate the roughness to the intensity of light scattering?</p>
| <p>To answer the second part: it's almost always done empirically by measuring a sample of the surface. The standard equation is known as the <a href="https://en.wikipedia.org/wiki/Bidirectional_reflectance_distribution_function" rel="nofollow">bidirectional reflectance distribution function</a>, which one uses to es... | 779 |
optics | Spherical wave solution for paraxial equation in far field region | https://physics.stackexchange.com/questions/685317/spherical-wave-solution-for-paraxial-equation-in-far-field-region | <p>I am reading this <a href="https://doi.org/10.1078/0030-4026-00177" rel="nofollow noreferrer">paper</a>. It consider the far-field region for the paraxial equation, <span class="math-container">$(\partial^2_x+\partial^2_y-2ik\partial_z)u(x,y,z)=0$</span>. Within the Rayleigh range, the solution will be described by ... | <p>It's a binomial expansion approximation to the <span class="math-container">$r$</span> in <span class="math-container">$e^{ikr}$</span>.
<span class="math-container">$$
r= \sqrt{x^2+y^2+z^2} = z\sqrt{ 1+ (x^2+y^2)/z^2}\\
\approx z\left(1+ \frac 12 (x^2+y^2)/z^2+\dots\right)
= z+ \frac 1{2z}(x^2+y^2)+ \ldots
$$</sp... | 780 |
optics | Can a light beam be used as a wire for telephony? | https://physics.stackexchange.com/questions/22382/can-a-light-beam-be-used-as-a-wire-for-telephony | <p>I've heard that Edison (maybe) invented a way to talk over a light beam. Is this true and how do you modulate the light beam?</p>
| <p><a href="http://en.wikipedia.org/wiki/Heliograph" rel="nofollow">Heliographs</a> permit communication over large distances with visible light, albeit with a rather low modulation frequency. It seems fairly clear that if you simply increase the switching rate you can create enough bandwidth to carry voice. As Ron has... | 781 |
optics | Moon landing: artificial generation of parallel beams of light | https://physics.stackexchange.com/questions/665059/moon-landing-artificial-generation-of-parallel-beams-of-light | <p>In <a href="https://youtu.be/dWBYAxhH3u4" rel="nofollow noreferrer">this video</a> of Adam ruins everything, Adam tries to debunk the claim that moon landing was fake using a central argument that we couldn't produce parallel beam of white light to mimic sunlight with computer graphics or lasers.</p>
<p><strong>But ... | <p><strong>Tl/Dr:</strong> Adam's handling is certainly incomplete, but there are interesting threads to tug on which were not covered in the video -- particularly in dealing with just how <em>massive</em> such a light source must be.</p>
<p>This is an interesting one. I don't think Adam and his guest covered everythi... | 782 |
optics | Transmittance through a reversed one-way mirror | https://physics.stackexchange.com/questions/509209/transmittance-through-a-reversed-one-way-mirror | <p>I am looking to use a half silvered one-way mirror to allow as much light and solar energy as possible into a room where there are highly reflective surfaces within the room - and I want to keep the energy from reflecting back outside - trap as much light/energy as I can in the room. That's why I am wondering what p... | <p>There is <a href="https://physics.stackexchange.com/questions/101380/how-does-a-one-sided-glass-work/101387#101387">no such thing</a> as a <a href="https://physics.stackexchange.com/questions/498482/optical-systems-that-make-a-ray-of-light-travel-a-different-way-to-and-from/">one</a>-<a href="https://physics.stackex... | 783 |
optics | Focal length calculation not matching intuition | https://physics.stackexchange.com/questions/700213/focal-length-calculation-not-matching-intuition | <p>I'm a computer engineering student working on my senior project that involves some optics. Illadvised though it may be, I'm contemplating building a telescope based on a simple achromatic refractor design for use in an automated astrophotography rig. I'm trying to work out how to build a compact telescope such as co... | <p>The question lacks some information. Specifically, the angular size of the Orion nebula, and the linear diameter of the camera sensor.</p>
<p>The Orion nebula is about <span class="math-container">$1$</span> arc degree in size (Google). This means that the angular size of the image will also be about <span class="... | 784 |
optics | Why is distance to an object inversely proportional to image size when using perspective projection? | https://physics.stackexchange.com/questions/700720/why-is-distance-to-an-object-inversely-proportional-to-image-size-when-using-per | <p><a href="https://www.cse.unr.edu/%7Ebebis/CS791E/Notes/PerspectiveProjection.pdf" rel="nofollow noreferrer">In this PDF</a>, it says the following about perspective projection:</p>
<blockquote>
<p>The distance to an object is inversely proportional to its image size.</p>
</blockquote>
<p>What causes this equasion? W... | <p>I think that the title of you post should be, <em>Why is <strong>distance to an object</strong> inversely proportional to image size when using perspective projection?</em></p>
<p><a href="https://i.sstatic.net/QtCKb.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/QtCKb.jpg" alt="enter image descripti... | 785 |
optics | "There aren’t seven colors in the rainbow" is this claim appropriate? | https://physics.stackexchange.com/questions/496318/there-aren-t-seven-colors-in-the-rainbow-is-this-claim-appropriate | <p>This <a href="https://www.quora.com/Why-are-there-7-colours-in-the-rainbow-while-there-are-only-3-or-4-colours-that-appear-to-us" rel="nofollow noreferrer">post</a> says</p>
<blockquote>
<p><code>There aren’t seven colors in the rainbow</code>, or any other specific number; Newton described seven colors in large ... | <p>Yes, the seven colours are an arbitrary classification. Our eyes are sensitive to three colour ranges, see <a href="https://en.wikipedia.org/wiki/Color_vision" rel="nofollow noreferrer">Color vision</a>.</p>
| 786 |
optics | Can electro-optic amplitude modulator generate sidebands? | https://physics.stackexchange.com/questions/572353/can-electro-optic-amplitude-modulator-generate-sidebands | <p>As the phase modulator, can electro-optic amplitude modulator generate sidebands?</p>
<p>I'm really confused now...</p>
<p>Please help me out.</p>
| 787 | |
optics | Can single-mode fiber collect incoherent light? | https://physics.stackexchange.com/questions/704813/can-single-mode-fiber-collect-incoherent-light | <p>I am now studying the rotational Doppler effect of partially coherent light, and I theoretically calculate that the cross-spectral density of completely incoherent light when coupled into a fiber is zero, but my instructor doesn't think so.</p>
| 788 | |
optics | I have been told that in an xyz plane.The normal on incident point is given,how do I visualise a normal which is like this | https://physics.stackexchange.com/questions/708118/i-have-been-told-that-in-an-xyz-plane-the-normal-on-incident-point-is-given-how | <p>Suppose I have a ray of light incident on a plane mirror in the general form of <span class="math-container">$$ai+bj-ck$$</span>. I have a normal that is along <span class="math-container">$$\frac{i+j}{√2}$$</span>. The question asks me to find the unit vector but that is not what I'm asking. My question is ,where s... | <p>I'm not sure what you're asking, but :<span class="math-container">$$\frac{\hat i + \hat j }{\sqrt{2}} = \frac{1}{\sqrt{2}} \hat i + \frac{1}{\sqrt{2}} \hat j$$</span></p>
<p><a href="https://i.sstatic.net/7kayY.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/7kayY.jpg" alt="enter image description h... | 789 |
optics | Can you see an image created by projector with bare eyes? | https://physics.stackexchange.com/questions/636236/can-you-see-an-image-created-by-projector-with-bare-eyes | <p>The question is as simple as I described in the title. Can you see an image created by a projector with your bare eyes? If so, where should you stand with respect to projector?</p>
| <p><strong>Don't try this because the light will be too bright to be safe for your eyes.</strong></p>
<p>The projector works by focusing an image onto the screen. If you remove the screen, then the image still exists that you can view if you are situated where the light can reach your eyes. The screen normally reflects... | 790 |
optics | Is the dimming of a phone screen under bright sunlight an example of destructive interference of visible light? | https://physics.stackexchange.com/questions/699093/is-the-dimming-of-a-phone-screen-under-bright-sunlight-an-example-of-destructive | <p>I have heard things like polarized phone screens being attributed to this effect but this wouldn't explain this phenomenon for non polarized phone screens under bright sunlight. Am I missing something?</p>
| <p>No. This is just because difference between white pixels and black pixels is overwhelmed by the sunlight that affects all pixels equally, and your eye can't tell the difference between white pixels and black pixels any more.</p>
<p>Interference of light waves (whether constructive or destructive) is not experienced ... | 791 |
optics | Why does looking through an LCD panel make things blurry? | https://physics.stackexchange.com/questions/242551/why-does-looking-through-an-lcd-panel-make-things-blurry | <p>When you take the back off an LCD panel and remove the backlight, you are left with a translucent panel. But when I look <em>through</em> the panel, even in its "clear" state, objects look blurry. Why is this? Shouldn't they just be dimmer, as the front polarizer blocks half of the light? Is diffraction to blame?</p... | <p>You want the backlight to be diffuse and even. That is not simple. If you look at a lamp of any kind you don't just see an evenly bright area. A diffuser is needed to make a uniformly bright spot. An everyday example of such a diffuser is fog. Or your hand if you look at a red light through it. Another good example ... | 792 |
optics | A mysterious phase difference | https://physics.stackexchange.com/questions/706047/a-mysterious-phase-difference | <p>Today my teacher was discussing the Poisson spot and gave a simple explanation for why there must be a bright spot on the axis of the disc when illuminated with parallel monochromatic light.</p>
<p>What he said was:</p>
<p>Say we instead have a circular aperture in an infinite plane, we know there must be a bright s... | <p>Your teacher was referring to Babinet's principle. It is often a good idea to fix your ideas on actual computation. You have an incident light field <span class="math-container">$\phi_i$</span> on the plane. As it crosses the plane, it either gets multiplied by <span class="math-container">$h_a=1{[r\leq R]}$</span> ... | 793 |
optics | Why the real image is always inverted while virtual image is always erect? | https://physics.stackexchange.com/questions/714724/why-the-real-image-is-always-inverted-while-virtual-image-is-always-erect | <p>While studying optics and the ray diagrams, I observed that the real images were always inverted and virtual were always erect. I have read several articles but haven't got any convincing answer. Someone please help !</p>
| <p>For a counterexample, for a thin lens:</p>
<p><span class="math-container">$$\frac{1}{p'}-\frac{1}{p}=\frac{1}{f'}
\quad\text{with}\quad
\begin{cases}
p=\overline{OA} & \text{object}\\
p'=\overline{OA'} & \text{image}
\end{cases}$$</span></p>
<p>The zoom factor is:</p>
<p><span class="math-container">$$\gamm... | 794 |
optics | Comparison of fabric bluing and blue glaciers | https://physics.stackexchange.com/questions/714740/comparison-of-fabric-bluing-and-blue-glaciers | <p>In learning about the effects of fabric bluing (it seems to mask yellowed fabric using a small amount of blue dye) I've wondered how this compares with the also-perceived blue of glaciers.</p>
| <p>I think they are different phenomena. The blue from glaciers is due to scattering of light and absorption. The longer wavelengths reds are absorbed while the blue light not absorbed as much continues to scatter forward.</p>
<p>For the fabric the blueing has a small amount of blue dye and is a complementary color for... | 795 |
optics | Partial Internal Reflection | https://physics.stackexchange.com/questions/524870/partial-internal-reflection | <p>What is partial internal reflection? Please elaborate with examples.</p>
<p>Why this phenomenon happens?
I searched on the internet but found nothing much. </p>
<p>Is this phenomenon involved in rainbow formation?
I think so because in the formation of a rainbow, TIR can't be involved. The geometry of a rain dro... | <p>when light goes from medium A to medium B you get a reflection, if medium B is transparent the reflection is partial(the other part is the light transmitted to B).
Internal or external is arbitrary.
Air is a medium, so normal reflection from a glass window is just another case of partial reflection.</p>
<p><a href=... | 796 |
optics | Do TN and IPS displays are subject to diffraction? | https://physics.stackexchange.com/questions/145949/do-tn-and-ips-displays-are-subject-to-diffraction | <p>Sometimes displays with the same resolution, diagonal and aspect ratio appear to have different level of sharpness .</p>
<p>In optics there is this concept of diffraction and if you can lower your diffraction the image gets sharper .</p>
<p>It's possible to get a simple explanation about why displays that appear t... | <p>If two displays have the same pixel sizes they will have the same amount of diffraction. The larger changes in image quality will come from a number of factors:</p>
<ol>
<li>The thickness of the display. The thicker the display, the lower the viewing angle</li>
<li>The LC material, this can have impact on the brigh... | 797 |
optics | Illuminance Formula | https://physics.stackexchange.com/questions/725265/illuminance-formula | <p><a href="https://math24.net/optimization-problems-physics.html#example6" rel="nofollow noreferrer">This page</a> says illuminance is
<span class="math-container">$$E=\frac{I}{L^2} cos \space \alpha$$</span></p>
<p><a href="https://www.toppr.com/ask/question/a-lamp-is-hanging-along-the-axis-of-a-circular-table-of-rad... | <p>A physical formula always applies to a given situation, and it is important to first check whether your situation matches the one this formula is meant for.</p>
<p>The formula without the <span class="math-container">$\cos \alpha$</span> term is meant for a situation <strong>where the light hits the surface in a rig... | 798 |
optics | Where did this equation come from ∠I+ ∠E = ∠A+ ∠D? | https://physics.stackexchange.com/questions/56624/where-did-this-equation-come-from-%e2%88%a0i-%e2%88%a0e-%e2%88%a0a-%e2%88%a0d | <p>$\angle I +\angle E=\angle A+\angle D$</p>
<p>Angle of incidence + angle of emergence = angle of prism (Normally $60^\circ$) + angle of deviation.</p>
<p>If their sum is not equal,we made personal error in doing an experiment with prism. Please make sense of this equation. </p>
| <p>The following diagram shows the prism with the incoming and outgoing light rays.</p>
<p><img src="https://i.sstatic.net/E4rrg.gif" alt="Prism"></p>
<p>If you follow the incident light ray in, it gets bent by an angle $\theta_1 = i- r_1$. If you follow the light ray where it leaves the glass, it gets bent again by ... | 799 |
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