The blackbody is a hollow enclosure with a pinhole to emit its radiations. The secure covering of the blackbody prevents the absorbed light from escaping. A blackbody is a solid closed unreal body that is inexistent. But lamp black, platinum black, and graphite-coated surfaces are non-ideal black bodies for laboratory purposes. An object with above 0.95 emissivities is an approximate blackbody. Besides, the hotter bodies emitting electromagnetic radiation under thermal equilibrium conditions are also considered partial black bodies.

1. Blackbody
Hot blackbody emissions
A blackbody is a rigid, closed
unreal body that can absorb all
electromagnetic radiation that
falls on it regardless of its
frequencies, but it reflects
none.
It is a perfect
emitter and
absorber of
thermal
radiations
following
Kirchhoff's law.
On heating, the blackbody releases all thermal
electromagnetic radiation that it absorbed
previously. These are blackbody radiations. A
blackbody radiates heat energies without affecting
the intervening medium. It has the highest emissive
power of all other bodies at that particular
temperature and wavelength conditions.
An ideal black body is an imaginary
perception of Gustav Kirchhoff.
The blackbody is inexistent.
An object with above 0.95
emissivities is an
approximate blackbody.
A graph between emissive power
and radiation wavelength at a
fixed temperature T is known as a
blackbody curve. At different
source temperatures, we observe
different black body curves.
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The black body spectrum depends only
on the temperature. And it is
independent of the shape, structure, and
composition of blackbody enclosure.
Factors affecting
blackbody emission
Temperature
Emissivity
Surface area
Laws governing
blackbody emission
Planck quantum law
Wien displacement law
Stefan-Boltzmann law