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MOSFET The metal–oxide–semiconductor field-effect transistor (MOSFET, MOS-FET, or MOS FET), also known as the metal–oxide–silicon transistor (MOS transistor, or MOS), is a type of insulated-gate field-effect transistor (IGFET) that is fabricated by the controlled oxidation of a semiconductor, typically silicon. The vol... | https://en.wikipedia.org/wiki?curid=40345 |
MOSFET The is considered to be possibly the most important invention in electronics, as the "workhorse" of the electronics industry and the "base technology" of the late 20th to early 21st centuries, having revolutionized modern culture, economy, society and daily life. A key advantage of a is that it requires almost n... | https://en.wikipedia.org/wiki?curid=40345 |
MOSFET Since MOSFETs can be made with either p-type or n-type semiconductors (PMOS or NMOS logic, respectively), complementary pairs of MOSFETs can be used to make switching circuits with very low power consumption, in the form of complementary MOS (CMOS) logic. The name "metal–oxide–semiconductor" (MOS) typically refe... | https://en.wikipedia.org/wiki?curid=40345 |
MOSFET In the course of trying to understand the mysterious reasons behind their failure to build a working FET, this led two members of Shockley's team, John Bardeen and Walter Brattain, to instead build a point-contact transistor, the first working transistor, in 1947, which was followed by Shockley's bipolar junctio... | https://en.wikipedia.org/wiki?curid=40345 |
MOSFET He investigated the surface properties of silicon semiconductors at Bell Labs, where he adopted a new method of semiconductor device fabrication, coating a silicon wafer with an insulating layer of silicon dioxide of controlled thickness, so that electricity could reliably penetrate to the conducting silicon bel... | https://en.wikipedia.org/wiki?curid=40345 |
MOSFET They fabricated the device in November 1959, and presented it as the "siliconsilicon dioxide field induced surface device" in early 1960, at the Solid-State Device Conference held at Carnegie Mellon University. The device is covered by two patents, each filed separately by Atalla and Kahng in March 1960. Operati... | https://en.wikipedia.org/wiki?curid=40345 |
MOSFET However, the generated significant interest at RCA Laboratories and Fairchild Semiconductor. In December 1960, Karl Zaininger and Charles Meuller at RCA Laboratories began fabricating an MOS device based on Atalla's device. Similarly based on Atalla's work, Chih-Tang Sah at Fairchild in late 1960 began building ... | https://en.wikipedia.org/wiki?curid=40345 |
MOSFET With its rapidly scaling miniaturisation, MOS technology became the focus of RCA, Fairchild, Intel and other semiconductor companies in the 1960s, fuelling the technological and economic growth of the early semiconductor industry based around California (including what later became known as Silicon Valley) as we... | https://en.wikipedia.org/wiki?curid=40345 |
MOSFET scaling and miniaturization (see "List of semiconductor scale examples") have been the primary factors behind the rapid exponential growth of electronic semiconductor technology since the 1960s, as the rapid miniaturization of MOSFETs has been largely responsible for the increasing transistor density, increasing... | https://en.wikipedia.org/wiki?curid=40345 |
MOSFET The has been called the most important transistor, the most important device in the electronics industry, the most important device in the computing industry, one of the most important developments in semiconductor technology, and possibly the most important invention in electronics. The has been the fundamental... | https://en.wikipedia.org/wiki?curid=40345 |
MOSFET There are also memory devices which contain at least a trillion MOS transistors, such as a 256GB microSD memory card, larger than the number of stars in the Milky Way galaxy. As of 2010, the operating principles of modern MOSFETs have remained largely the same as the original first demonstrated by Mohamed Atalla... | https://en.wikipedia.org/wiki?curid=40345 |
MOSFET Unfortunately, many semiconductors with better electrical properties than silicon, such as gallium arsenide, do not form good semiconductor-to-insulator interfaces, and thus are not suitable for MOSFETs. Research continues on creating insulators with acceptable electrical characteristics on other semiconductor m... | https://en.wikipedia.org/wiki?curid=40345 |
MOSFET The traditional metal–oxide–semiconductor (MOS) structure is obtained by growing a layer of silicon dioxide () on top of a silicon substrate, commonly by thermal oxidation and depositing a layer of metal or polycrystalline silicon (the latter is commonly used). As the silicon dioxide is a dielectric material, it... | https://en.wikipedia.org/wiki?curid=40345 |
MOSFET This structure with p-type body is the basis of the n-type MOSFET, which requires the addition of n-type source and drain regions. The MOS capacitor structure is the heart of the MOSFET. Consider a MOS capacitor where the silicon base is of p-type. If a positive voltage is applied at the gate, holes which are at... | https://en.wikipedia.org/wiki?curid=40345 |
MOSFET In the case of a p-type bulk, inversion happens when the intrinsic energy level at the surface becomes smaller than the Fermi level at the surface. One can see this from a band diagram. Remember that the Fermi level defines the type of semiconductor in discussion. If the Fermi level is equal to the Intrinsic lev... | https://en.wikipedia.org/wiki?curid=40345 |
MOSFET A is based on the modulation of charge concentration by a MOS capacitance between a "body" electrode and a "gate" electrode located above the body and insulated from all other device regions by a gate dielectric layer. If dielectrics other than an oxide are employed, the device may be referred to as a metal-insu... | https://en.wikipedia.org/wiki?curid=40345 |
MOSFET At larger gate bias still, near the semiconductor surface the conduction band edge is brought close to the Fermi level, populating the surface with electrons in an "inversion layer" or "n-channel" at the interface between the p region and the oxide. This conducting channel extends between the source and the drai... | https://en.wikipedia.org/wiki?curid=40345 |
MOSFET If the channel region between the gate dielectric and the buried oxide region is very thin, the channel is referred to as an ultrathin channel region with the source and drain regions formed on either side in or above the thin semiconductor layer. Other semiconductor materials may be employed. When the source an... | https://en.wikipedia.org/wiki?curid=40345 |
MOSFET In weak inversion where the source is tied to bulk, the current varies exponentially with formula_4 as given approximately by: where formula_8 = current at formula_9, the thermal voltage formula_10 and the slope factor "n" is given by: with formula_12 = capacitance of the depletion layer and formula_13 = capacit... | https://en.wikipedia.org/wiki?curid=40345 |
MOSFET By working in the weak-inversion region, the MOSFETs in these circuits deliver the highest possible transconductance-to-current ratio, namely: formula_20, almost that of a bipolar transistor. The subthreshold "I–V curve" depends exponentially upon threshold voltage, introducing a strong dependence on any manufac... | https://en.wikipedia.org/wiki?curid=40345 |
MOSFET Since the drain voltage is higher than the source voltage, the electrons spread out, and conduction is not through a narrow channel but through a broader, two- or three-dimensional current distribution extending away from the interface and deeper in the substrate. The onset of this region is also known as pinch-... | https://en.wikipedia.org/wiki?curid=40345 |
MOSFET If λ is taken as zero, the resulting infinite output resistance can simplify circuit analysis, however this may lead to unrealistic circuit predictions, particularly in analog circuits. As the channel length becomes very short, these equations become quite inaccurate. New physical effects arise. For example, car... | https://en.wikipedia.org/wiki?curid=40345 |
MOSFET This change in channel strength by application of reverse bias is called the 'body effect'. Simply put, using an nMOS example, the gate-to-body bias "V" positions the conduction-band energy levels, while the source-to-body bias V positions the electron Fermi level near the interface, deciding occupancy of these ... | https://en.wikipedia.org/wiki?curid=40345 |
MOSFET Another line is drawn parallel to the channel for the gate. The "bulk" or "body" connection, if shown, is shown connected to the back of the channel with an arrow indicating pMOS or nMOS. Arrows always point from P to N, so an NMOS (N-channel in P-well or P-substrate) has the arrow pointing in (from the bulk to ... | https://en.wikipedia.org/wiki?curid=40345 |
MOSFET However, these symbols are often drawn with a "T" shaped gate (as elsewhere on this page), so it is the arrowhead which must be relied upon to indicate the source terminal. For the symbols in which the bulk, or body, terminal is shown, it is here shown internally connected to the source (i.e., the black arrowhea... | https://en.wikipedia.org/wiki?curid=40345 |
MOSFET Their original devices also had a gate oxide thickness of 100 nm. However, the nMOS devices were impractical, and only the pMOS type were practical working devices. A more practical NMOS process was developed several years later. NMOS was initially faster than CMOS, thus NMOS was more widely used for computers i... | https://en.wikipedia.org/wiki?curid=40345 |
MOSFET In 1978, Hitachi introduced the twin-well CMOS process, which allowed CMOS to match the performance of NMOS with less power consumption. The twin-well CMOS process eventually overtook NMOS as the most common semiconductor manufacturing process for computers in the 1980s. By the 1970s1980s, CMOS logic consumed ov... | https://en.wikipedia.org/wiki?curid=40345 |
MOSFET Metal–insulator–semiconductor field-effect-transistor, or "MISFET", is a more general term than "MOSFET" and a synonym to "insulated-gate field-effect transistor" (IGFET). All MOSFETs are MISFETs, but not all MISFETs are MOSFETs. The gate dielectric insulator in a MISFET is silicon dioxide in a MOSFET, but other... | https://en.wikipedia.org/wiki?curid=40345 |
MOSFET The voltage rating of the transistor is a function of the doping and thickness of the N-epitaxial layer (see cross section), while the current rating is a function of the channel width (the wider the channel, the higher the current). In a planar structure, the current and breakdown voltage ratings are both a fun... | https://en.wikipedia.org/wiki?curid=40345 |
MOSFET The MOS capacitor is widely used as a storage capacitor in memory chips, and as the basic building block of the charge-coupled device (CCD) in image sensor technology. In DRAM (dynamic random-access memory), each memory cell typically consists of a and MOS capacitor. The thin-film transistor (TFT) is a type of d... | https://en.wikipedia.org/wiki?curid=40345 |
MOSFET The ISFET is a special type of with a gate at a certain distance, and where the metal gate is replaced by an ion-sensitive membrane, electrolyte solution and reference electrode. By the mid-1980s, numerous other sensors had been developed, including the gas sensor FET (GASFET), surface accessible FET (SAFET), ch... | https://en.wikipedia.org/wiki?curid=40345 |
MOSFET Vacuum-tube tetrodes, using a screen grid, exhibit much lower grid-plate capacitance and much higher output impedance and voltage gains than triode vacuum tubes. These improvements are commonly an order of magnitude (10 times) or considerably more. Tetrode transistors (whether bipolar junction or field-effect) d... | https://en.wikipedia.org/wiki?curid=40345 |
MOSFET A quantum field-effect transistor (QFET) or quantum well field-effect transistor (QWFET) is a type of that takes advantage of quantum tunneling to greatly increase the speed of transistor operation. Semiconductor sub-micrometer and nanometer electronic circuits are the primary concern for operating within the no... | https://en.wikipedia.org/wiki?curid=40345 |
MOSFET These advantages include improvement of reliability by reducing unwanted surface inversion at the gate edges that occurs in the standard MOSFET. Since the gate edges are enclosed in ELT, there is no gate oxide edge (STI at gate interface), and thus the transistor off-state leakage is reduced considerably. Low-po... | https://en.wikipedia.org/wiki?curid=40345 |
MOSFET Radio-frequency amplifiers up to the UHF spectrum use transistors as analog signal and power amplifiers. Radio systems also use MOSFETs as oscillators, or mixers to convert frequencies. devices are also applied in audio-frequency power amplifiers for public address systems, sound reinforcement and home and autom... | https://en.wikipedia.org/wiki?curid=40345 |
MOSFET This was followed by the development of clean rooms to reduce contamination to levels never before thought necessary, and coincided with the development of photolithography which, along with surface passivation and the planar process, allowed circuits to be made in few steps. Mohamed Atalla first proposed the co... | https://en.wikipedia.org/wiki?curid=40345 |
MOSFET In 1967, Bell Labs researchers Robert Kerwin, Donald Klein and John Sarace developed the self-aligned gate (silicon-gate) MOS transistor, which Fairchild Semiconductor researchers Federico Faggin and Tom Klein used to develop the first silicon-gate MOS IC. With its high scalability, and much lower power consumpt... | https://en.wikipedia.org/wiki?curid=40345 |
MOSFET The first multi-chip microprocessors, the Four-Phase Systems AL1 in 1969 and the Garrett AiResearch MP944 in 1970, were developed with multiple MOS LSI chips. The first commercial single-chip microprocessor, the Intel 4004, was developed by Federico Faggin, using his silicon-gate MOS IC technology, with Intel en... | https://en.wikipedia.org/wiki?curid=40345 |
MOSFET That extent is defined by the operating frequency: as frequencies increase, the input impedance of the MOSFETs decreases. The MOSFET's advantages in digital circuits do not translate into supremacy in all analog circuits. The two types of circuit draw upon different features of transistor behavior. Digital circu... | https://en.wikipedia.org/wiki?curid=40345 |
MOSFET MOSFETs' ideal characteristics regarding gate current (zero) and drain-source offset voltage (zero) also make them nearly ideal switch elements, and also make switched capacitor analog circuits practical. In their linear region, MOSFETs can be used as precision resistors, which can have a much higher controlled ... | https://en.wikipedia.org/wiki?curid=40345 |
MOSFET Mixed-transistor devices are called bi-FETs (bipolar FETs) if they contain just one BJT-FET and BiCMOS (bipolar-CMOS) if they contain complementary BJT-FETs. Such devices have the advantages of both insulated gates and higher current density. In the late 1980s, Asad Abidi pioneered RF CMOS technology, which uses... | https://en.wikipedia.org/wiki?curid=40345 |
MOSFET While examining the characteristics of MOS technology, he found it was capable of building capacitors, and that storing a charge or no charge on the MOS capacitor could represent the 1 and 0 of a bit, while the MOS transistor could control writing the charge to the capacitor. This led to his development of a sin... | https://en.wikipedia.org/wiki?curid=40345 |
MOSFET One of the earliest influential consumer electronic products enabled by MOS LSI circuits was the electronic pocket calculator, as MOS LSI technology enabled large amounts of computational capability in small packages. In 1965, the Victor 3900 desktop calculator was the first MOS LSI calculator, with 29 MOS LSI c... | https://en.wikipedia.org/wiki?curid=40345 |
MOSFET Advances in MOS technology has been the most important contributing factor in the rapid rise of network bandwidth in telecommunication networks, with bandwidth doubling every 18 months, from bits per second to terabits per second (Edholm's law). MOS sensors, also known as sensors, are widely used to measure phys... | https://en.wikipedia.org/wiki?curid=40345 |
MOSFET The MOS active-pixel sensor (APS) was developed by Tsutomu Nakamura at Olympus in 1985. The CMOS active-pixel sensor was later developed by Eric Fossum and his team at NASA's Jet Propulsion Laboratory in the early 1990s. MOS image sensors are widely used in optical mouse technology. The first optical mouse, inve... | https://en.wikipedia.org/wiki?curid=40345 |
MOSFET They are widely used for automotive, industrial and communications systems in particular. Power MOSFETs are commonly used in automotive electronics, particularly as switching devices in electronic control units, and as power converters in modern electric vehicles. The insulated-gate bipolar transistor (IGBT), a ... | https://en.wikipedia.org/wiki?curid=40345 |
MOSFET To reduce the resulting leakage current, the insulator can be made thinner by choosing a material with a higher dielectric constant. To see how thickness and dielectric constant are related, note that Gauss's law connects field to charge as: with "Q" = charge density, κ = dielectric constant, ε = permittivity of... | https://en.wikipedia.org/wiki?curid=40345 |
MOSFET The source-to-body and drain-to-body junctions are the object of much attention because of three major factors: their design affects the current–voltage ("I–V") characteristics of the device, lowering output resistance, and also the speed of the device through the loading effect of the junction capacitances, and... | https://en.wikipedia.org/wiki?curid=40345 |
MOSFET Historically, the difficulties with decreasing the size of the have been associated with the semiconductor device fabrication process, the need to use very low voltages, and with poorer electrical performance necessitating circuit redesign and innovation (small MOSFETs exhibit higher leakage currents and lower o... | https://en.wikipedia.org/wiki?curid=40345 |
MOSFET For example, one approach to size reduction is a scaling of the that requires all device dimensions to reduce proportionally. The main device dimensions are the channel length, channel width, and oxide thickness. When they are scaled down by equal factors, the transistor channel resistance does not change, while... | https://en.wikipedia.org/wiki?curid=40345 |
Caesium standard The caesium standard is a primary frequency standard in which the photon absorption by transitions between the two hyperfine ground states of caesium-133 atoms are used to control the output frequency. The first caesium clock was built by Louis Essen in 1955 at the National Physical Laboratory in the U... | https://en.wikipedia.org/wiki?curid=40858 |
Caesium standard "" At its 1997 meeting the BIPM added to the previous definition the following specification: ""This definition refers to a caesium atom at rest at a temperature of 0 K."" The BIPM restated this definition in its 26th conference (2018), ""The second is defined by taking the fixed numerical value of the... | https://en.wikipedia.org/wiki?curid=40858 |
Caesium standard When the atom is irradiated with electromagnetic radiation having an energy corresponding to the energetic difference between the two sub-levels the radiation is absorbed and the atom is excited, going from the sub-level to the one. After a small fraction of a second the atom will re-emit the radiation... | https://en.wikipedia.org/wiki?curid=40858 |
Dielectric A dielectric (or dielectric material) is an electrical insulator that can be polarized by an applied electric field. When a dielectric material is placed in an electric field, electric charges do not flow through the material as they do in an electrical conductor but only slightly shift from their average eq... | https://en.wikipedia.org/wiki?curid=41026 |
Dielectric The term insulator is generally used to indicate electrical obstruction while the term dielectric is used to indicate the energy storing capacity of the material (by means of polarization). A common example of a dielectric is the electrically insulating material between the metallic plates of a capacitor. Th... | https://en.wikipedia.org/wiki?curid=41026 |
Dielectric The susceptibility of a medium is related to its relative permittivity "ε" by So in the case of a vacuum, The electric displacement D is related to the polarization density P by In general, a material cannot polarize instantaneously in response to an applied field. The more general formulation as a function ... | https://en.wikipedia.org/wiki?curid=41026 |
Dielectric In the presence of an electric field the charge cloud is distorted, as shown in the top right of the figure. This can be reduced to a simple dipole using the superposition principle. A dipole is characterized by its dipole moment, a vector quantity shown in the figure as the blue arrow labeled "M". It is the... | https://en.wikipedia.org/wiki?curid=41026 |
Dielectric Examples of phenomena that can be so modeled include: Dipolar polarization is a polarization that is either inherent to polar molecules (orientation polarization), or can be induced in any molecule in which the asymmetric distortion of the nuclei is possible (distortion polarization). Orientation polarizatio... | https://en.wikipedia.org/wiki?curid=41026 |
Dielectric The molecular vibration frequency is roughly the inverse of the time it takes for the molecules to bend, and this distortion polarization disappears above the infrared. Ionic polarization is polarization caused by relative displacements between positive and negative ions in ionic crystals (for example, NaCl)... | https://en.wikipedia.org/wiki?curid=41026 |
Dielectric All cells in animal body tissues are electrically polarized – in other words, they maintain a voltage difference across the cell's plasma membrane, known as the membrane potential. This electrical polarization results from a complex interplay between ion transporters and ion channels. In neurons, the types o... | https://en.wikipedia.org/wiki?curid=41026 |
Dielectric Because permittivity indicates the strength of the relation between an electric field and polarization, if a polarization process loses its response, permittivity decreases. relaxation is the momentary delay (or lag) in the dielectric constant of a material. This is usually caused by the delay in molecular p... | https://en.wikipedia.org/wiki?curid=41026 |
Dielectric Debye relaxation is the dielectric relaxation response of an ideal, noninteracting population of dipoles to an alternating external electric field. It is usually expressed in the complex permittivity "ε" of a medium as a function of the field's frequency "ω": where "ε" is the permittivity at the high frequen... | https://en.wikipedia.org/wiki?curid=41026 |
Dielectric An example of a paraelectric material of high dielectric constant is strontium titanate. The LiNbO crystal is ferroelectric below 1430 K, and above this temperature it transforms into a disordered paraelectric phase. Similarly, other perovskites also exhibit paraelectricity at high temperatures. Paraelectric... | https://en.wikipedia.org/wiki?curid=41026 |
Dielectric Systems such as have a paraelectric–ferroelectric transition just below ambient temperature, providing high tunability. Such films suffer significant losses arising from defects. Commercially manufactured capacitors typically use a solid dielectric material with high permittivity as the intervening medium be... | https://en.wikipedia.org/wiki?curid=41026 |
Dielectric It consists of a "puck" of ceramic that has a large dielectric constant and a low dissipation factor. Such resonators are often used to provide a frequency reference in an oscillator circuit. An unshielded dielectric resonator can be used as a dielectric resonator antenna (DRA). From 2002 to 2004, the Army R... | https://en.wikipedia.org/wiki?curid=41026 |
Dielectric (A high vacuum can also be a useful, nearly lossless dielectric even though its relative dielectric constant is only unity.) Solid dielectrics are perhaps the most commonly used dielectrics in electrical engineering, and many solids are very good insulators. Some examples include porcelain, glass, and most p... | https://en.wikipedia.org/wiki?curid=41026 |
Drop (liquid) A drop or droplet is a small column of liquid, bounded completely or almost completely by free surfaces. A drop may form when liquid accumulates at the lower end of a tube or other surface boundary, producing a hanging drop called a pendant drop. Drops may also be formed by the condensation of a vapor or ... | https://en.wikipedia.org/wiki?curid=41068 |
Drop (liquid) Since the length of this boundary is the circumference of the tube, the force due to surface tension is given by where "d" is the tube diameter. The mass "m" of the drop hanging from the end of the tube can be found by equating the force due to gravity (formula_3) with the component of the surface tension... | https://en.wikipedia.org/wiki?curid=41068 |
Drop (liquid) The measurement of both adhesion forms can be done with the Centrifugal Adhesion Balance (CAB). The CAB uses a combination of centrifugal and gravitational forces to obtain any ratio of lateral and normal forces. For example, it can apply a normal force at zero lateral force for the drop to fly off away f... | https://en.wikipedia.org/wiki?curid=41068 |
Drop (liquid) These oscillating bubbles are responsible for most liquid sounds, such as running water or splashes, as they actually consist of many drop-liquid collisions. Reducing the surface tension of a body of liquid makes possible to reduce or prevent noise due to droplets falling into it. This would involve addin... | https://en.wikipedia.org/wiki?curid=41068 |
Drop (liquid) Macrodrops will be 'flattened' by gravity and the height of the droplet will be reduced. Raindrop sizes typically range from 0.5 mm to 4 mm, with size distributions quickly decreasing past diameters larger than 2-2.5 mm. Scientists traditionally thought that the variation in the size of raindrops was due ... | https://en.wikipedia.org/wiki?curid=41068 |
Gel A gel is a semi-solid that can have properties ranging from soft and weak to hard and tough. Gels are defined as a substantially dilute cross-linked system, which exhibits no flow when in the steady-state. By weight, gels are mostly liquid, yet they behave like solids due to a three-dimensional cross-linked network... | https://en.wikipedia.org/wiki?curid=41207 |
Gel This allows them to contribute more to viscosity in their stretched state, because the stretched-out polymer takes up more space. This is also the reason gel hardens. See polyelectrolyte for more information. A hydrogel is a network of polymer chains that are hydrophilic, sometimes found as a colloidal gel in which... | https://en.wikipedia.org/wiki?curid=41207 |
Gel The liquid can be, for example, an organic solvent, mineral oil, or vegetable oil. The solubility and particle dimensions of the structurant are important characteristics for the elastic properties and firmness of the organogel. Often, these systems are based on self-assembly of the structurant molecules. (An examp... | https://en.wikipedia.org/wiki?curid=41207 |
Gel A wide range of nanoparticles, such as carbon-based, polymeric, ceramic, and metallic nanomaterials can be incorporated within the hydrogel structure to obtain nanocomposites with tailored functionality. Nanocomposite hydrogels can be engineered to possess superior physical, chemical, electrical, and biological pro... | https://en.wikipedia.org/wiki?curid=41207 |
Gel A review article on the subject discusses the use of hydrogels for nucleus pulposus replacement, cartilage replacement, and synthetic tissue models. Many substances can form gels when a suitable thickener or gelling agent is added to their formula. This approach is common in manufacture of wide range of products, f... | https://en.wikipedia.org/wiki?curid=41207 |
Hydroxyl ion absorption is the absorption in optical fibers of electromagnetic waves, including the near-infrared, due to the presence of trapped hydroxyl ions remaining from water as a contaminant. The hydroxyl (OH) ion, can penetrate glass during or after product fabrication, resulting in significant attenuation of d... | https://en.wikipedia.org/wiki?curid=41248 |
Lambert's cosine law In optics, says that the radiant intensity or luminous intensity observed from an ideal diffusely reflecting surface or ideal diffuse radiator is directly proportional to the cosine of the angle "θ" between the direction of the incident light and the surface normal. The law is also known as the cos... | https://en.wikipedia.org/wiki?curid=41306 |
Lambert's cosine law This means that although the radiance of the surface depends on the angle from the normal to the illuminating source, it will not depend on the angle from the normal to the observer. For example, if the moon were a Lambertian scatterer, one would expect to see its scattered brightness appreciably d... | https://en.wikipedia.org/wiki?curid=41306 |
Lambert's cosine law The maximum rate of photon emission per unit solid angle is along the normal, and diminishes to zero for "θ" = 90°. In mathematical terms, the radiance along the normal is "I" photons/(s·m·sr) and the number of photons per second emitted into the vertical wedge is "I" "dΩ" "dA". The number of photo... | https://en.wikipedia.org/wiki?curid=41306 |
Lambert's cosine law In general, the luminous intensity of a point on a surface varies by direction; for a Lambertian surface, that distribution is defined by the cosine law, with peak luminous intensity in the normal direction. Thus when the Lambertian assumption holds, we can calculate the total luminous flux, formul... | https://en.wikipedia.org/wiki?curid=41306 |
Lambert's cosine law The phenomenon can be used when creating mouldings, with the effect of creating light- and dark-shaded stripes on a structure or object without having to change the material or apply pigment. The contrast of dark and light areas gives definition to the object. Mouldings are strips of material with ... | https://en.wikipedia.org/wiki?curid=41306 |
Magneto-optic effect A magneto-optic effect is any one of a number of phenomena in which an electromagnetic wave propagates through a medium that has been altered by the presence of a quasistatic magnetic field. In such a medium, which is also called gyrotropic or gyromagnetic, left- and right-rotating elliptical polar... | https://en.wikipedia.org/wiki?curid=41343 |
Magneto-optic effect The ε becomes anisotropic, a 3×3 matrix, with complex off-diagonal components, depending of course on the frequency ω of incident light. If the absorption losses can be neglected, ε is a Hermitian matrix. The resulting principal axes become complex as well, corresponding to elliptically-polarized l... | https://en.wikipedia.org/wiki?curid=41343 |
Magneto-optic effect Then, if we let g lie in the "z" direction for simplicity, the ε tensor simplifies to the form: Most commonly, one considers light propagating in the "z" direction (parallel to g). In this case the solutions are elliptically polarized electromagnetic waves with phase velocities formula_11 (where μ ... | https://en.wikipedia.org/wiki?curid=41343 |
Magneto-optic effect If this wave interacts with a material at which the horizontal component (green sinusoid) travels at a different speed than the vertical component (blue sinusoid), the two components will fall out of the 90 degree phase difference (required for circular polarization) changing the Kerr Ellipticity A... | https://en.wikipedia.org/wiki?curid=41343 |
Numerical aperture In optics, the numerical aperture (NA) of an optical system is a dimensionless number that characterizes the range of angles over which the system can accept or emit light. By incorporating index of refraction in its definition, NA has the property that it is constant for a beam as it goes from one m... | https://en.wikipedia.org/wiki?curid=41432 |
Numerical aperture In air, the angular aperture of the lens is approximately twice this value (within the paraxial approximation). The NA is generally measured with respect to a particular object or image point and will vary as that point is moved. In microscopy, NA generally refers to object-space NA unless otherwise ... | https://en.wikipedia.org/wiki?curid=41432 |
Numerical aperture The approximation holds when the numerical aperture is small, but it turns out that for well-corrected optical systems such as camera lenses, a more detailed analysis shows that is almost exactly equal to even at large numerical apertures. As Rudolf Kingslake explains, "It is a common error to suppos... | https://en.wikipedia.org/wiki?curid=41432 |
Numerical aperture The working -number is defined by modifying the relation above, taking into account the magnification from object to image: where is the working -number, is the lens's magnification for an object a particular distance away, is the pupil magnification, and the NA is defined in terms of the angle of th... | https://en.wikipedia.org/wiki?curid=41432 |
Numerical aperture Far away from the narrowest part of the beam, the spread is roughly linear with distance—the laser beam forms a cone of light in the "far field". The relation used to define the NA of the laser beam is the same as that used for an optical system, but is defined differently. Laser beams typically do n... | https://en.wikipedia.org/wiki?curid=41432 |
Numerical aperture For step-index multimode fiber in a given medium, the acceptance angle is determined only by the indices of refraction of the core, the cladding, and the medium: where is the refractive index of the medium around the fiber, is the refractive index of the fiber core, and is the refractive index of the... | https://en.wikipedia.org/wiki?curid=41432 |
Numerical aperture The number of bound modes, the mode volume, is related to the normalized frequency and thus to the NA. In multimode fibers, the term "equilibrium numerical aperture" is sometimes used. This refers to the numerical aperture with respect to the extreme exit angle of a ray emerging from a fiber in which... | https://en.wikipedia.org/wiki?curid=41432 |
Avogadro constant The Avogadro constant, usually denoted by "N" or "L" is the factor that, multiplied by the amount of substance in a sample, measured in moles, gives the number of constituent particles (usually molecules, atoms or ions) in that sample. Its unit is the reciprocal of mole, and it is defined as It is nam... | https://en.wikipedia.org/wiki?curid=41545 |
Avogadro constant For example, since the molar volume of water in ordinary conditions is about 18 mL/mol, the volume occupied by one molecule of water is about mL, or about 30 Å (cubic angstroms). For a crystaline substance, it similarly relates its molar volume (in mL/mol), the volume of the repeating unit cell of th... | https://en.wikipedia.org/wiki?curid=41545 |
Avogadro constant However, in its 26th Conference, the BIPM adopted a different approach: effective 20 May 2019, it defined the Avogadro number as the exact integer , and redefined the mole as the amount of a substance under consideration that contains "N" constituent particles of the substance. Under the new definitio... | https://en.wikipedia.org/wiki?curid=41545 |
Avogadro constant This value, the number density "n" of particles in an ideal gas, is now called the Loschmidt constant in his honor, and is related to the Avogadro constant, "N", by where "p" is the pressure, "R" is the gas constant, and "T" is the absolute temperature. Because of this work, the symbol "L" is sometime... | https://en.wikipedia.org/wiki?curid=41545 |
Avogadro constant By this definition, the common rule of thumb "one gram of matter contains "N" nucleons" was exact for carbon-12, but slightly inexact for other elements and isotopes. On the other hand, one mole of any substance contained exactly as many molecules as one mole of any other substance. As a consequence o... | https://en.wikipedia.org/wiki?curid=41545 |
Avogadro constant For example, if quantities of a substance are measured in pound-mole (lb-mol), then the "N" is lb-mol. If the ounce-mole (oz-mol) is used instead, "N" is oz-mol. However, these units are hardly used nowadays. The Avogadro constant, "N" is related to other physical constants and properties. | https://en.wikipedia.org/wiki?curid=41545 |
Rubidium standard A rubidium standard or rubidium atomic clock is a frequency standard in which a specified hyperfine transition of electrons in rubidium-87 atoms is used to control the output frequency. It is the most inexpensive, compact, and widely produced atomic clock, used to control the frequency of television s... | https://en.wikipedia.org/wiki?curid=41674 |
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