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Glossary P-Z
Photometer
A device so designed that it furnishes the ratio, or a function of theratio, of the radiant power of two electromagnetic beams. These two beams may be separated in time , space, or both. Photometric Linearity The ability of a photometric system to yield a linear relationship between the radiant power incident on ist detector and some measurable quantity provided by the system. Plane grating The grating has a plane substrate and straight and equidistant grooves. Reflection grating The grating is used in reflection which the incident light is getting a directional reversal. Reflective coatings are preferred aluminium and gold. Refelectance The ratio of reflected to incident radiation. (A practical definition requires that basic term be modified by adjectives to indicate the spectral and geometric weighting of the incident and reflected radiation). Replication Profile-true multiplication method to mass-produce diffraction gratings. The grating structure is replicated in epoxy or uv cured adhesive. Usually the replicated gratings are duplicates of a higher generation (copies of copies) but their efficiency comes closest to that of the master gratings. Resolution capability Minimum spacing of 2 wavelengths separable by Resolving power a grating, proportional to the grating area and inversely proportional to the wavelength Resolution, Spectral The ratio/?, where the wavelength region being examined, and ? is the separation of two distinguishable absorption bands . Resolution also defined as /?, where and ? refer to the wavenumber scale. Sinusoidal grating The grating groove profile is sinusoidal. Spectrograph An instrument with one slit that uses photography to obtain a record of a special range simulaneously. Spectrometer An instrument with an entrance slit and one or more exit slits, with which measurements are made eigther by scanning the spectral range point by point or by simultaneous measuements at several spectral positions. Spectrophotometer A spectrometer with associated equipment so designed that it furnishes the ratio or a function of the ratio of the radiant power of two beams as a function of spectral position. Spectral Band Width The wavelength or frequency interval of the radiation leaving the exit slit of a mono-chromator between limits set at a radiant power level half way between the continuous background and the peak of an emission line or an absorption band of negligible intrinsic width. Transmission grating The grating is used in transmission. Transmittance The ratio of radiant power transmitted by the sample to the radiant power incident on the sample. Ultraviolet Pertaining to the region of the electromagnetic spectrum from approximately 10 to 380 nm. The term ultraviolet without further qualification usually refers to the region from 200 to 380 nm. Visible Relating to radiant energy in the electromagnetic spectral range visible to the normal human eye, approx 380 to 780 nm. Wavelength The distance measurred along the line of propagation between two points that are in phase on adjacent waves. Wavenumber The number of Waves per unitlength.
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