Many approaches can potentially quantify radiation absorption, with key examples following.
Which among them practitioners use varies by field and technique, often due simply to the convention.
Precise measurements of the absorbance at many wavelengths allow the identification of a substance via absorption spectroscopy, where a sample is illuminated from one side, and the intensity of the light that exits from the sample in every direction is measured.
Understanding and measuring the absorption of electromagnetic radiation has a variety of applications.
In scientific literature is known a system of mirrors and lenses that with a laser "can enable any material to absorb all light from a wide range of angles.
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). Upon striking the sample,
photons
that match the
energy gap
of the
molecules
present (green light in this example) are
absorbed
, exciting the molecules. Other photons are scattered (not shown here) or transmitted unaffected; if the radiation is in the visible region (400–700 nm), the transmitted light appears as the complementary color (here red). By recording the
attenuation
of light for various wavelengths, an
absorption spectrum
can be obtained.
Rough plot of Earth's atmospheric
transmittance
(or opacity) to various wavelengths of electromagnetic radiation, including
visible light
