What is a Blackbody? A black body is an idealization in physics that pictures a body that absorbs all electromagnetic radiation incident on it irrespective of its frequency or angle. Through the second law of thermodynamics that a body always tries to stay in thermal equilibrium. To stay in thermal equilibrium, a black body must emit radiation at the same rate as it absorbs and so it must also be a good emitter of radiation, emitting electromagnetic waves of as many frequencies as it can absorb i.e. all the frequencies. The black body radiation is governed by the Planck radiation law. The Planck radiation law explains the various electromagnetic radiations emitted by a black body at thermal equilibrium at a fixed temperature. Through the Planck radiation law, we were able to understand that radiation emitted by a body is completely independent of the body’s shape, size or composition and is dependent only on the Temperature of the body.