Question

A perfect black body is a
(A) Perfect absorber of radiation.
(B) Perfect emitter of radiation.
(C) Perfect reflection of radiation.
(D) Perfect refractor of radiation.

Answer 1

Hint Here we know the description of the black body and the principle of the mechanism so that we can study the perfect black body so that we can know that radiation is released in all frequency ranges by the ideal black body at thermal equilibrium, emitting more energy as the frequency increases.
Useful formula:
Plank law,
\[\;E{\text{ }} = {\text{ }}\sigma {T^4}\;\]
 where \[E\] is the radiant heat emitted from a unit of area per unit time, $T $ is the absolute temperature.

Complete step by step answer
Given by,
Perfect black body,
A black body is an idealized physical body that absorbs all electromagnetic radiation that exists, irrespective of the frequency or angle of incidence. The black body name is given because it absorbs radiation at all wavelengths, not because black-body radiation can be released only by a black body. On the opposite, a white body is one with a' rough surface' that completely and uniformly represents all incident rays in all directions.
In thermal equilibrium, a black body emits electromagnetic black-body radiation (that is, at a constant temperature). The radiation is emitted in accordance with the Planck law which means that it has a temperature-determined spectrum.
There are two notable properties of an ideal black body in thermal equilibrium:
It is an ideal emitter: emitting as much or more thermal radiative energy at any frequency as any other body at the same temperature.
It is a diffuse emitter: the energy is radiated isotropically, regardless of direction, measured per unit area perpendicular to the direction.
Hence,
A body that absorbs all the radiation on it is considered to be a perfectly black body, a good absorber is always a good radiation emitter hands, perfectly black bodies are always good radiation emitters.

Thus, option A is the correct answer.

Note Here, one that absorbs all incoming light and does not reflect any, is a perfect black body. Such an item will tend to be completely black at room temperature. However, a blackbody can begin to glow with thermal radiation if heated to a high temperature.