How heated matter emits light and why its spectrum helped begin quantum physics.
What is black-body radiation?
Black-body radiation is the electromagnetic radiation emitted by an ideal object that absorbs all incoming radiation.
Its spectrum depends only on temperature, not on the object's material.
What did classical physics miss?
Classical models predicted too much energy at short wavelengths, a problem called the ultraviolet catastrophe.
Max Planck resolved the mismatch by proposing that energy exchange occurs in discrete amounts related to frequency: E = h f.
Why is it important?
The problem helped begin quantum physics. Black-body ideas also support thermal imaging, astronomy, furnace design, climate measurement and the interpretation of stellar spectra.
A real object is not a perfect black body, but the model is a powerful reference.
What else follows?
As temperature rises, total emitted power increases and the peak of the spectrum shifts toward shorter wavelengths.
These patterns turn radiation into a way to infer temperature and composition without touching an object.
Future
Better infrared sensors and models will improve medicine, energy systems, climate observation and space science. The historical lesson is that a precise measurement can reveal when a successful theory has reached its limits.
Ai disclosure: written with the help of AI (ChatGPT). You are encouraged to point out errors and omissions.  
