How is it possible that,photon doesn't have mass but it have momentum??

1 Answer
Dec 17, 2017

Newton associated momentum with mass, but relativity changed it all.

Explanation:

Einstein's famous equation relating energy E, mass m and the speed of light c, has a hidden detail. The mass term increases as velocity increases.

E=mc2

It can be written as:

E2=(m0c2)2+p2c2

Where m0 is rest mass and p is momentum.

In the case of a photon it has no mass so m0=0.

So, E=pc. A photon has energy which can be calculated from its frequency ν and Planck's constant h.

E=hν

So as a photon has energy it also has momentum:

p=hνc