Question

What is black body in physics how is it realised in practice?

Answer 1

Black body is body that absorbes all the radiation that falls on it and then releases all the radiation slowly
It can be thought as a black box with a hole in it. If radiation falls on it its goes inside and then by multiple reflection it is absorbed...

Answer 2

Answer:

A black body is a metal sphere coated with platinum - black and a hole on its surface.

A perfect black - body emits and absorbs all radiations .

However a perfect black - body does not exist .

Hope it helps :)