You might have observed that boiled milk becomes cold when kept at room temperature, while a chilled bottle becomes warm kept at the same room temperature. Have you ever wondered how do objects become colder or warmer? This answer lies in the phenomenon of �Transfer of Heat�. Heat flows from a hotter object to a colder object. Let us learn the transfer of heat by radiation.

Radiation

You would have experienced that when you come out in the Sun, you feel warm. Have you ever thought that how does the heat from the sun reaches us? You have learned in Conduction and Convection that heat is transferred from one object to other through a medium but Sun is situated very far from the earth and air exists only up to 300 kilometers from the surface of the earth.

The space between the Sun and the earth is occupied by Vacuum. From the Sun, heat comes to us by another process known as Radiation. Radiation is a process in which heat is transferred from one object to another even in the absence of the medium.

Also, the intervening medium does not get heated The transfer of heat by radiation does not require any medium. Heat can be transferred by radiation even in the absence of a medium. Actually, heat is radiated by all hot bodies.

When this heat falls on some object, a part of it is reflected, a part is absorbed and some part may be transmitted. That is why you feel warm when you stand in the sun.

Let�s see some examples of radiation:

1. When we sit in front of a bonfire, we get heat by this process.
2. A hot utensil kept away from the flame cools down as it radiates heat.
3. Our body also radiates heat to the surroundings

Read More: What is Conduction? Transfer Of Heat By Conduction | Conductors