Question

Assertion : The second postulate of special relativity refers to the velocity of light in vacuum. 

Reason : Cerenkov radiation results r.l'hen particles move through transparent matter at a speed greater than the speed of light in that medium. It does not violate the second postulate of special relativity.

(a) Both A and R are true and R is the correct explanation of A

(b) Both A and R are true but R is not correct explanation of A

(c) A is true but R is false

(d) A and R are false

Answer 1

The correct option is (b).

Explanation:

The second postulate of special theory of relativity states that no material particle can cross the speed of light in vacuum. Cerenkov radiation occurs when some particles move through a transparent medium such as water with a speed more than the speed of light in the medium. So the existence of Cerenkov radiation tells us that the speed of light in a transparent medium can be crossed by a material particle in some circumstances. But this does not violate the second postulate of special theory of relativity as it deals with the speed in vacuum.