What does cause the rolling sound of thunder ?

Explain the formation of thunder.

Assertion: The flash of lightening is sees before the sound of thunder is heard. Reason: Speed of sound is greater than speed of light.

Statement-1 : The flash of lightening is seen before the sound of thunder is heard Statement-2 : The sound of thunder is produced after the flash of lightening.

What is the cause for production of sound ? Can sound propagate in vacuum?

What does not change when sound enters from one medium to another?

Which does not cause pollution?

Explain why there is usually a time interval between observing a flash of lighning and hearing its thunder. Account for the rolling sound which is often produced when the thunder is heard.