How does a perfect black body interact with radiation?

A perfect black body absorbs all incident radiation and emits radiation at a maximum rate for its temperature.

A perfect black body is an idealised object in physics that is a perfect absorber and emitter of radiation. This means that it absorbs all electromagnetic radiation, regardless of wavelength or angle of incidence, without reflecting or transmitting any of it. Because it absorbs all the radiation, it appears completely black when it is at a lower temperature than its surroundings.

When it comes to emitting radiation, a perfect black body does so at the maximum possible rate for a given temperature. This emission is described by Planck's law, which states that the amount and type of radiation emitted by a black body depend solely on its temperature. The radiation emitted covers a range of wavelengths, with the peak wavelength shifting to shorter wavelengths as the temperature increases. This is why objects like stars, which are very hot, emit visible light, while cooler objects emit infrared radiation.

The concept of a perfect black body is crucial in understanding thermal radiation and energy transfer. For instance, the Sun can be approximated as a black body, which helps scientists predict the spectrum of sunlight. Similarly, black body radiation principles are used in designing thermal cameras and understanding the cosmic microwave background radiation, which provides evidence for the Big Bang theory.

In summary, a perfect black body is a theoretical object that perfectly absorbs and emits radiation, making it a fundamental concept in the study of thermal physics and radiation.