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

1 Answer
Phillip E. ยท Mark C.
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=mc^2

It can be written as:

E^2=(m_0c^2)^2 +p^2c^2

Where m_0 is rest mass and p is momentum.

In the case of a photon it has no mass so m_0=0.

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

E=h nu

So as a photon has energy it also has momentum:

p=(h nu)/c

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