ABSTRACT
This chapter considers spectral distribution of the continuous radiation emitted by a blackbody, i.e., the dependence of the intensity of the blackbody radiation on the wavelength of the radiation. Blackbody is an object that absorbs completely all radiation falling on it, independent of its frequency, wavelength, and intensity. Formulation of the correct theoretical approach to calculate the spectrum of the blackbody radiation was a major challenge in theoretical physics during the late 19th century. In 1900, Strutt Rayleigh calculated the energy density distribution I (λ) of the radiation emitted by the blackbody box at absolute temperature T. The experimental results on the spectrum of X-rays, properties of photoelectric effect, Compton scattering, atomic spectra, and the spectrum of the blackbody radiation indicate that something is seriously wrong with the wave theory of light. The radiation emitted by a body that is heated is called thermal radiation. All bodies emit and absorb such radiation.
