When electromagnetic radiation hits a body, three different effects occur: transmission, absorption and reflection. The relative proportions of radiant energy that are reflected, absorbed or transmitted depend on both the material properties of the body and the wavelength. The reflectance, i.e. the proportion of the electromagnetic radiation energy that is reflected by the body, is between 0 and 1 (or 0% and 100%). Since no other effects can occur, the following applies:
Where α stands for the degree of absorption, ρ for the reflectance and τ for the transmittance.
The dependence of the reflectance on the wavelength is among other things the cause of the color vision. For example, since chlorophyll in plants absorbs radiation in the red and blue wavelengths and reflects radiation in the green wavelength range, plants appear green.