How heat transfer occurs through radiation in absence of a medium?

1. All objects possess thermal energy due to their temperature T(T > 0 K). 

2. The rapidly moving molecules of a hot body emit EM waves travelling with the velocity of light. These are called thermal radiations. 

3. These carry energy with them and transfer it to the low-speed molecules of a cold body on which they fall. 

4. This results in an increase in the molecular motion of the cold body and its temperature rises. 

5. Thus transfer of heat by radiation is a two fold process-the conversion of thermal energy into waves and reconversion of waves into thermal energy by the body on which they fall.