3 Black Body Radiation

A body whose temperature is above absolute zero emits radiant energy. The power radiated (in W) can be calculated according to the Stefan-

4ATeQe 

Boltzmann law.

e is the emissivity of surface (varies between 0 and 1) and depends on:

• nature of surface • temperature of

surface • wavelength of the

radiation being i d b b d

Our interest here is the variation in intensity (W m2) as a f nction of temperat re and em tte or a sor e u u wavelength. To eliminate the “nature of the surface” effect, we will consider the radiation emission from what is called a black body.