In physics, absorption of electromagnetic radiation is how matter takes up a photon's energy—and so transforms electromagnetic energy into internal energy of the absorber.
Rough plot of Earth's atmospheric transmittance (or opacity) to various wavelengths of electromagnetic radiation, including visible light
Refractive index
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In optics, the refractive index, often denoted n, is the ratio of the speed of light in vacuum to the speed of light in a given optical medium, n=c/v. The refractive index determines how much the path
Thomas Young coined the term index of refraction in 1807.
Diamonds have a very high refractive index of 2.417.
A split-ring resonator array arranged to produce a negative index of refraction for microwaves
In optical mineralogy, thin sections are used to study rocks. The method is based on the distinct refractive indices of different minerals.