QS Study

Prevost applied the idea of thermal equilibrium to radiation. According to him, the rate at which a body radiates or absorbs heat depends on the nature of its surface, its temperature and the temperature of the surroundings. The total amount of heat radiated by a body increases as its temperature rises. A body at a higher temperature radiates more heat energy to the surroundings than it receives from the surroundings. That is why we feel warm when we stand before the furnace.

Similarly, a body at a lower temperature receives more heat energy than it loses to the surroundings. That is why we feel cold when we stand before an ice block.

Thus the rise or fall of temperature is due to the exchange of heat radiation. When the temperature of the body is the same as that of surroundings, the exchanges of heat do not stop. In such a case, the amount of heat energy radiated by the body is equal to the amount of heat energy absorbed by it.

A body will stop emitting radiation only when it is at absolute zero. Example: 0 K or -273° C. At this temperature the kinetic energy of the molecule is zero.

Therefore, Prevost’s theory states that all bodies emit thermal radiation at all temperatures above absolute zero, irrespective of the nature of the surroundings.