Photonics Dictionary

Characterizes an Earth-orbiting satellite whose orbit plane is near polar and positioned at an altitude that allows it to pass over every spot on the Earth at identical local sun time twice a day.

Controlled beam technology that introduces beams of sunlight through holes in a roof that are relayed throughout the building by a series of mirrors and lenses. Ideally, cool lighting is obtained by...

An instrument consisting essentially of a photoelectric cell filtered to respond to a specified wavelength region, an amplifier of sufficient gain to provide power enough to control movement of a...

A device that measures the intensity of photochemically active radiation, particularly from the sun. One form of this instrument determines the fluorescence initiated by the radiation.

A type of solar eclipse that occurs when the sun is at perihelion and the moon is at apogee. Because the apparent size of the moon is insufficient to cover the sun, the outer edge of the solar disc...

The point to which the extension of the straight line, reaching from the sun to the observer's eye after penetrating the atmosphere of the Earth, is projected.

The point of a planet or comet's orbit that is farthest from the sun.

The unit generally used to express distances within the solar system, and sometimes to measure interstellar distances. Technically, one astronomical unit is the mean distance between the Earth and...

1. That action occurring when light passes through an optical interface at other than normal incidence, i.e., refraction. 2. The curving of a path of light that passes close by a massive object, due...

Name originally given to the sun's infrared radiation by Sir William Herschel in his Philosophical Transactions of 1800.

A layer between the corona and the photosphere of the sun; its emission is overwhelmed by light emitted by the underlying, denser photosphere.

A test used to measure the degree of fading of different colored materials, especially those involving organic dyes, which tend to fade when exposed to bright sunlight, to a damp atmosphere or to...

A telescope in which a mask occults the solar disk, generating an artificial eclipse and allowing observation and recording of the sun's corona.

Solar regions characterized by low density and open magnetic fields where high-speed solar wind streams originate. Originally believed to be "M'' regions, coronal holes are the precursors of the...

Phase shift in electromagnetic signals caused by daily variations in the ionosphere, often during sunrise or sunset.

Uniform measure of time based on dynamics law and calculated according to planetary orbital paths; specifically, Earth's orbit about the sun.

The dark absorption lines observed in the spectrum of the photosphere of the sun. There are thousands of these lines, the most prominent of which were observed and named by Fraunhofer early in the...

A Fresnel lens is a type of optical lens that consists of a series of concentric grooves or steps carved into a flat, thin piece of transparent material, typically plastic or glass. This design...

A device having a plane mirror so mounted that it can be set to reflect sunlight into a piece of laboratory equipment. It is driven by a clock to compensate for the sun's daily motion around the pole...

A system of Japanese origin that utilizes Fresnel lenses and a fiber optic network to transmit sunlight to otherwise inaccessible areas.

Inertial fusion energy (IFE) refers to a proposed method of generating electricity by harnessing the energy released from the fusion of light atomic nuclei, typically isotopes of hydrogen, through a...

The graph of a curve describing the spectral irradiance of extraterrestrial sunlight.

A dark band that may appear in the field of crossed Nicol prisms with a powerful source such as the sun because the light is not strictly parallel and is not extinguished immediately.

A collector for photovoltaic power generation that consists of a thin plate that strongly absorbs sunlight striking its faces and luminesces efficiently. A large fraction of the luminescence is...

One of two types of solar time - the other being apparent solar time - the mean solar time is the time measured by the average hour angle position of the sun in the sky compiled over a period of one...

Mie scattering, named after the German physicist Gustav Mie, refers to the scattering of electromagnetic radiation (such as light) by spherical particles. Unlike Rayleigh scattering, which is...

A light source, such as the sun or an incandescent lamp, that freely penetrates ordinary glass bulbs and emits in the near-ultraviolet (wavelengths ranging from about 300 to 400 nm). A mercury vapor...

In physics, nuclear fusion refers to the process in which two atomic nuclei come together to form a heavier nucleus, releasing a large amount of energy. This process powers the sun and other stars...

A measure of the optical path length for light traveling from the sun or other celestial source through Earth's atmosphere to sea-level relative to the optical path length traveled by light from the...

Optoelectronics is a branch of electronics that focuses on the study and application of devices and systems that use light and its interactions with different materials. The term "optoelectronics" is...

The term photochemical pertains to chemical processes or reactions that are initiated or influenced by the absorption of light. Photochemical reactions involve the interaction of light, often in the...

Photochromic refers to a property exhibited by certain materials, typically organic compounds or dyes, which undergo reversible changes in color when exposed to light. Specifically, photochromic...

The apparent surface of the sun or a star from which light appears to radiate.

Phototherapy is a medical treatment that involves the use of light to treat various conditions, particularly those related to the skin or mood disorders. There are different types of phototherapies,...

Phototoxicity refers to the harmful effects caused by exposure to light, particularly intense or ultraviolet (UV) light, on living cells or organisms. This phenomenon is often associated with the...

A photovoltaic cell, commonly known as a solar cell, is a semiconductor device that directly converts light energy into electrical energy through the photovoltaic effect. The photovoltaic effect is...

Photovoltaic (PV) refers to a technology that converts sunlight directly into electricity using semiconductors. The term "photovoltaic" is derived from the words "photo," meaning light, and...

A device used in solar systems to direct mirror-reflected sunlight to a heat absorber and heat-driven engine, which turns a generator to produce electricity.

Polarization refers to the orientation of oscillations in a transverse wave, such as light waves, radio waves, or other electromagnetic waves. In simpler terms, it describes the direction in which...

Quantum efficiency (QE) is a measure of the effectiveness with which a device or system, typically in the context of photonics or electronics, converts incoming photons (light) into a useful output...

Rayleigh scattering is a phenomenon that occurs when light waves interact with particles or molecules that are much smaller than the wavelength of the light. It is named after the British scientist...

A handheld navigational instrument used to measure the elevation angle of celestial bodies such as the sun. An image of the sun is viewed through a small telescope via two plane mirrors so that any...

A compact high-pressure light source in which an electrical discharge between electrodes spaced no more than 12 mm apart occurs in a xenon or other gas medium, providing a visible light resembling a...

A group of solar cells that are electrically contacted and physically arranged so that they may be oriented in the direction of the sun simultaneously.