This page is optimized for large screens. Zooming may cause some display problems.

glossary

Black body: theoretical object absorbing all the electromagnetic energy it receives, which creates thermal agitation; at equilibrium ( i.e. at constant temperature), all the energy absorbed is re-emitted in electromagnetic radiation also called thermal radiation
Wavelength ( of a light wave ): distance between two consecutive identical states of the electric ( or magnetic ) field
Spectral power density: power density per unit wavelength