Transmission of light
Certain types of transparent media, like coloured filters or coloured glass, absorb certain wavelengths of light within a beam, and allow others to pass through or be transmitted.
When a white light source like a flashlight shines through a red coloured filter, light with many long wavelengths, very few middle wavelengths and few short wavelengths is transmitted by the filter.
A source of white light from the flashlight on the left passes through a red-coloured filter. The transmitted beam contains not many short wavelengths, a few but not many middle wavelengths and lots of long wavelengths. Diagram courtesy of Robin Kingsburgh & David Briggs.
See also: Filter.
