Physics

Black-body radiation

Prof Partha Pratim Sarma, Dipankar Swargiary

Professor | Oxford University

Published on Jul 14, 2026

Black-body radiation

Abstract

 

Black-body radiation is the thermal electromagnetic radiation emitted from a body in thermodynamic equilibrium with its environment. A black body is an idealized opaque and non-reflective body. The radiation emitted is a continuous spectrum over all possible radiation wavelengths that depends only on the body's temperature.[1][2][3][4]

A perfectly-insulated enclosure which is in thermal equilibrium internally contains black-body radiation and will emit it through a hole made in its wall, provided the hole is small enough to have a negligible effect upon the equilibrium. The thermal radiation spontaneously emitted by many ordinary objects can be approximated as black-body radiation.

Of particular importance, although planets and stars (including the Earth and Sun) are neither in thermal equilibrium with their surroundings nor perfect black bodies, black-body radiation is still a good first approximation for the energy they emit.[5]

Author Information

  • Prof Partha Pratim Sarma

    Professor, Oxford University

    partha@gmail.com

    India, Assam, Udalguri, 123456

Co-authors

  • Dipankar Swargiary

    Professor, Oxford University