All the objects, which are above the absolute zero gives out (liberates) some energy. This energy travels mainly in the form of electro-magnetic waves (infra-red waves or light waves) and these waves can travel through empty space. If any object absorbs (receives) these waves, they heat up those objects. This process is knows as thermal radiation.
Example 1: On earth sun is the main source of energy.
Earth receives the energy from the sun due to thermal radiation.
Why people are advised to wear white clothes in summer?
A. White clothes absorb the radiation quickly.
B. White clothes do not absorb the radiation quickly.
C. White clothes are very soft.
D. White clothes emit radiation quickly.
Correct answer is B.
Step 1: Black cloth absorbs more radiation, so "A" is not correct choice.
Step 2: White objects will not absorb the radiation. Hence we will not absorb more radiation by wearing white clothes. "B" is the correct choice.
Step 3: All the white clothes are not soft, so "C" is not the correct choice.
Step 4: Black body only emits radiation quickly. White bodies will not emit the radiation quickly. So "D" is not correct choice.