Radiation is a form of heat transfer in which particles are not required to carry heat energy. Heat is transferred in the form of waves from hot objects in all directions. Radiation can occur in a vacuum, but conduction and convection require the presence of matter. Electromagnetic waves travelling at the speed of light constitute radiation.

Radiation is defined as the transfer of heat from one location to another by means of electromagnetic waves.
The heat energy of the sun is transferred to us in the form of radiation. All bodies above \(0\) degrees Celsius emit radiation. Radiation is absorbed by some objects, while others reflect it.
Solar radiation
Radiation in daily life:
  • Heat is reflected well by white or light-coloured clothes. They keep us cool during summer.
  • The base of cooking utensils is blackened because the black surface absorbs more heat from the surrounding.
  • The aeroplane's surface is highly polished because it helps to reflect most of the heat radiation from the sun.
We can see all three modes of heat transfer while firing wood. Due to conduction, heat will be transferred from one end of the wood to the other. The air near the wood will warm up and push out the air above it this happens due to convection. Our hands will be warm because heat reaches us in the form of radiation.