Define thermal radiation and radiant energy and explain Prevost's theory of heat exchange.

(N/A) Thermal radiation: All substances emit electromagnetic waves of certain definite frequencies depending on their temperature. This radiation is called thermal radiation.
Radiant energy: The energy associated with the electromagnetic waves in thermal radiation is called radiant energy.
Prevost's theory of heat exchange: According to this theory,every body at any temperature (above $0 \ K$) continuously emits thermal radiation to its surroundings and simultaneously absorbs radiation from its surroundings.
$1$. The rate of emission of thermal radiation depends on the temperature of the body. As the temperature increases,the rate of emission increases.
$2$. If the rate of emission is greater than the rate of absorption,the temperature of the body decreases.
$3$. If the rate of emission is less than the rate of absorption,the temperature of the body increases.
$4$. When the body reaches thermal equilibrium with its surroundings,the rate of emission becomes equal to the rate of absorption,and the temperature of the body remains constant.