What is a black body in physics?

A black body in physics is defined as an idealized physical object that absorbs all incoming electromagnetic radiation, regardless of the frequency or angle of incidence. This means that a black body not only absorbs radiation perfectly but also emits radiation in accordance with Planck's law when it is in thermal equilibrium.

Planck's law describes the spectral density of electromagnetic radiation emitted by a black body in thermal equilibrium at a given temperature. It indicates how much radiation is emitted at different wavelengths and shows that a black body is capable of emitting distribution of energy across a range of wavelengths, with a peak dependent on its temperature. This characteristic makes black bodies a crucial concept in various fields, including thermodynamics, quantum physics, and astronomy, providing a reference point for real materials.

The incorrect options highlight misunderstandings about black bodies. For instance, a black body does not reflect radiation (as mentioned in the first option), and it is not merely a high-temperature light-emitting material (as suggested in the third option) since it can emit radiation at all temperatures. Additionally, the description of a black body as a perfect insulator that cannot transfer heat (the fourth option) is inaccurate, as black bodies are excellent absorbers and emitters of thermal radiation, which is a mechanism