Question

A hot and a cold body are kept in vacuum separated from each other. What will be the reason for the decrease in temperature of the hot body?
A. conduction
B. radiation
C. convection
D. the temperature of bodies remain unchanged

Answer 1

Hint: Heat transfer from an object which is having a high temperature to another object having a lower temperature, if these objects are not in direct physical contact with each other or they are separated in space is generally defined as the heat radiation. This will help you in answering this question.

Complete step by step answer:
Heat transfer from an object which is having a high temperature to another object having a lower temperature, if these objects are not in direct physical contact with each other or they are separated in space is generally defined as the heat radiation. Thermal radiation is happening through a vacuum or any transparent medium (solid or fluid or gas). It will be the transfer of energy with the help of photons in the electromagnetic waves. In the question it has been mentioned that two bodies with different temperatures are separated by a distance in vacuum. Therefore the heat transfer happening here will be radiation itself.

So, the correct answer is “Option B”.

Note: All of the physical substances in solid, liquid, or gaseous states will be able to emit energy through a process of electromagnetic radiation due to the vibrational and rotational movement of their molecules and atoms. The intensity of such energy flux is dependent upon the temperature of the body and the nature of the surface. The radiation happens at all temperatures. Even though the rate of emission will be increasing with the increase in temperature.