Photonics Dictionary: R

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

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

An instrument used to detect radioactive materials: alpha particles or helium nuclei; beta particles or free electrons; and gamma rays, which are x-rays of very short wavelength. They may be detected...

Ratiometry is a technique used in various scientific fields, particularly in analytical chemistry and biochemistry, to measure concentrations or quantities by comparing the intensity of two different...

When a lens system with a circular aperture is free of aberrations, the image of a point object will appear as a disc of finite size surrounded by concentric rings. When two points are separated such...

An instrument that spectrally analyzes the flux reflected from a material. The reflected flux may be total, diffuse or specular. Often the instrument measures the reflectance factor instead of the...

A reflection grating is an optical component that consists of a series of closely spaced, parallel reflecting surfaces or grooves. These grooves are typically ruled or etched onto a flat substrate or...

Reflectance spectroscopy is a technique used to analyze the reflective properties of materials across various wavelengths of the electromagnetic spectrum. By measuring the reflectance of light from a...

An instrument for measuring reflectance.

An instrument used to measure the refractive index of solids and liquids. Several types exist, the most common being the Abbe refractometer.

Resonance can be defined in various contexts, including physics, chemistry, and music. Here are definitions for resonance in a few different fields: Physics: In physics, resonance refers to the...

A resonator is a device or system that exhibits resonance, which is a phenomenon that occurs when an external force or stimulus is applied at a specific frequency, causing the system to oscillate...

A reticle, also known as a reticule or graticule, is a pattern or set of markings placed in the focal plane of an optical instrument, such as a microscope, telescope, riflescope, or camera, to...

Retroreflection is a phenomenon in optics where light is reflected back toward its source, typically in a direction nearly parallel to the direction from which it originated. This occurs due to the...

A reflecting prism that is rhomboidal in shape. It has two parallel transmitting faces, and two parallel reflecting faces; the latter are oblique to the former (usually but not necessarily at...