3. Some key elements
It was defined by Max planck in 19th century
He got noble prize in 1918 for black body radiation
4. What is black body radiation
Black-body radiation is the thermal electromagnetic radiation
within, or surrounding, a body in thermodynamic equilibrium
with its environment, emitted by a black body (an idealized
opaque, non-reflective body). It has a specific, continuous
spectrum of wavelengths, inversely related to intensity, that
depend only on the body's temperature, which is assumed, for
the sake of calculations and theory, to be uniform and constant.
5. Explanation of black body radiation
Blackbody radiation refers to the spectrum of light emitted by any heated element. The
spectral intensity of blackbody radiation peaks at a frequency that increases with the
temperature of the emitting body: room temperature objects (about 300 K) emit radiation
with a peak intensity in the far infrared; radiation from toaster filaments and light bulb
filaments (about 700 K and 2,000 K, respectively) also peak in the infrared, though their
spectra extend progressively into the visible; while the 6,000 K surface of the Sun emits
blackbody radiation that peaks in the center of the visible range. In the late 1890s,
calculations of the spectrum of blackbody radiation based on classical electromagnetic
theory and thermodynamics could not duplicate the results of careful measurements. In fact,
the calculations predicted the absurd result that, at any temperature, the spectral intensity
increases without limit as a function of frequency.
