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Particular light frequencies give rise to sharply defined bands on the scale which can be thought of as fingerprints. For example, the element sodium has a very characteristic double yellow band known as the Sodium D-lines at 588.9950 and 589.5924 nanometers, the color of which will be familiar to anyone who has seen a low pressure sodium vapor ...
An overview of absorption of electromagnetic radiation.This example shows the general principle using visible light as a specific example. A white light source—emitting light of multiple wavelengths—is focused on a sample (the pairs of complementary colors are indicated by the yellow dotted lines).
Absorbance is defined as "the logarithm of the ratio of incident to transmitted radiant power through a sample (excluding the effects on cell walls)". [1] Alternatively, for samples which scatter light, absorbance may be defined as "the negative logarithm of one minus absorptance, as measured on a uniform sample". [2]
DMax and DMin refer to the maximum and minimum density that can be produced by the material. The difference between the two is the density range. [1] The density range is related to the exposure range (dynamic range), which is the range of light intensity that is represented by the recording, via the Hurter–Driffield curve.
A densitometer is a device that measures the degree of darkness (the optical density) of a photographic or semitransparent material or of a reflecting surface. [1] The densitometer is basically a light source aimed at a photoelectric cell . [ 2 ]
Planck opacity (also known as Planck-Mean-Absorption-Coefficient [1]) uses the normalized Planck black-body radiation energy density distribution, (), as the weighting function, and averages directly: = () = (), where is the Stefan–Boltzmann constant.
m is the optical mass or airmass factor, a term approximately equal (for small and moderate values of θ) to , where θ is the observed object's zenith angle (the angle measured from the direction perpendicular to the Earth's surface at the observation site).
An electromagnetic wave propagating along a path C has the phase shift over C as if it was propagating a path in a vacuum, length of which, is equal to the optical path length of C. Thus, if a wave is traveling through several different media, then the optical path length of each medium can be added to find the total optical path length. The ...