How does radiation transfer heat energy?

1 Answer
Jul 28, 2016

Radiation transfers heat energy through photons.


All matter with a temperature above the absolute temperature of #0 K# emits thermal radiation, which is an electromagnetic radiation generated by the internal collision of particles in a matter. Like all electromagnetic radiations, thermal radiation propagates through space without requiring a medium, which is why heat from the Sun can reach Earth.

Thermal radiations are produced due to the inter-atomic collisions between charged particles, which carry energy away from the radiating object in the form of electromagnetic radiation. This energy can be absorbed by other distant objects, which cause the internal energy of particles of that object to increase. As a result, the particles in that object move faster and collide more often, which releases energy as heat, increasing the temperature of the object.

Unlike other methods of heat transfer like conduction or convection, thermal radiation can be concentrated on a focal point using reflective mirrors, which is used in solar power generation.

The rate of heat energy through radiation can be calculated using the Stefan-Boltzmann Constant.
#Q = epsilon sigma T^4#
where #Q# is heat flux, #epsilon# is the emissivity and #sigma# is the Stefan-Boltzmann constant and #T# is the absolute temperature.

The transfer of heat between two radiant bodies can be calculated using
#Q = epsilon sigma (T_a^4-T_b^4)#.