Photonics Dictionary: R

The emission and/or propagation of energy through space or through a medium in the form of either waves or corpuscular emission.

Half the vertex angle of the cone of light emitted by a fiber.

An instrument used to recognize and identify incident radiation by the ionizing or stimulating properties of the radiation.

Any of the many devices used to detect the presence of radiation from a specific region of the electromagnetic spectrum.

The detection and measurement of nuclear and x-ray radiation.

The average length in a specific material in which a relativistic charged particle will lose 67 percent of its energy by bremsstrahlung.

A mode in an optical waveguide whose fields are transversely oscillatory everywhere external to the waveguide. It exists even in the limit of zero wavelength.

Relative power distribution as a function of position or angle.

The force exerted on a surface by radiation.

Also known as radiation thermometer. A pyrometer in which the radiant intensity from the source to be measured is used to calculate its temperature. The usual detector is a thermocouple, thermopile...

The temperature of a complete radiator that has a total radiant emittance identical to that of an unknown resource.

A thermocouple that is used in infrared spectroscopy to detect a sample's infrared emittance. See thermocouple.

That process by which radiation spontaneously emitted by a volume of optical materials is resonantly reabsorbed within the same volume before it escapes. This effect is manifested in a reduction in...

The film used in photographic dosimetry to record the types and amounts of ionizing radiation, such as x-rays and gamma rays, present in an area for a set interval of time. The negative produced by...

Plates of glass containing as many heavy metal oxides as can be dissolved in the glass without causing devitrification. The glass is yellow, very heavy and has a high refractive index. It is almost...

The radiation emitted in semiconductors when electrons in the conduction band recombine with holes in the valence band. If population inversion occurs between portions of the valence and conduction...

That radiation emitted by an atom or molecule that has the same frequency as that of an incident particle; e.g., a photon. It generally involves a transition to the lowest energy level of the atom or...

A unit of energy absorbed from ionizing radiation, equal to 100 ergs per gram of irradiated material.

An acronym for radioactive detection, identification and computation. The term refers to the detection and measurement of the intensity of emitted nuclear radiation.

Pertaining to electromagnetic radiation, with the contributions at all wavelengths of interest weighted equally.

The energy passed on as electromagnetic radiation; e.g., radio, heat or light waves.

Infrared radiation emitted from a source that is not heated sufficiently to give off visible radiation.

The detection and analysis of naturally formed extraterrestrial electromagnetic radiation within the radio frequency range of the spectrum.

An instrument designed to collect naturally formed extraterrestrial electromagnetic radiation within the radio frequency range of the spectrum in amounts sufficient to be measured.

A photographic process using x-ray radiation or the g-rays of radioactive materials.

The study of radioactive substances and high-energy radiations such as x-rays and g-rays.

Incapable of being penetrated by any form of radiation.

Capable of being penetrated by some form of radiation.

The luminescence displayed when particular minerals are irradiated with β-rays and g-rays, after being exposed to nuclear radiation.

That element of a spectrum line in scattered radiation having a frequency equal to that of the corresponding incident radiation, due to ordinary or Rayleigh scattering.

A photographic method used to obtain an image of a subject by means of its reflectance of incident ultraviolet radiation. An ultraviolet source is used to irradiate the subject, while the reflected...

A microscope that uses a reflecting objective; often used with ultraviolet or infrared radiation.

Return of radiation by a surface, without change in wavelength. The reflection may be specular, from a smooth surface; diffuse, from a rough surface or from within the specimen; or mixed, a...

The term reflective is an adjective that describes the ability of a surface or material to reflect light or other forms of radiation. It implies the capability of bouncing back or redirecting...

The ratio of the intensity of the total radiation reflected from a surface to the total incident on that surface.

A wave of radiation that has undergone refraction.

The steady state of temperature exhibited by a material that has absorbed and emitted radiation equally.

The unit of the dose of any radiation that produces the same biological effect as one roentgen of x-ray.

Remote sensing is a method of data collection and observation where information about objects, areas, or phenomena on Earth's surface is gathered from a distance, typically using sensors onboard...

In atomic fluorescence spectroscopy, fluorescence emitted by an atom at a spectral line of a wavelength identical to that of the stimulating radiation.

The fluorescent emission spectrum emitted by certain substances following the irradiation of one of these substances with light that is of the same wavelengths as its fluorescence.

An obsolete term once used to describe a unit of radiation dosage.