# what is the mass of photon ? According to de broglie equation it is almost zero ….... but according to relativity, the mass of a particle moving at the speed of light is infinity(consider the particle as photon here ) . What is the real mass of electron ? pls explain how it is derived .

#
what is the mass of photon ? According to de broglie equation it is almost zero ….... but according to relativity, the mass of a particle moving at the speed of light is infinity(consider the particle as photon here ) . What is the real mass of electron ? pls explain how it is derived .

## 3 Answers

8 years ago

The photon is massless. It has energy but no mass.

The de Broglie equation for a relativisitic particleis given by:

The rest mass is zero for the photon as the velocity of the particle approaches the velocity of light.

The real mass of electron is approximately

It is derived from the charge by mass ratio experiment.

Regards

Sumit

8 years ago

In case of photon, if it moves with speed of light(which it does), it doesn’t have infinity mass.Why?

m

_{v}=m

_{0}/(1-v

^{2}/c

^{2})^0.5 , where m

_{v}is mass of particle when the object is moving with ‘v’ velocity. m

_{0}is the rest mass.

For a photon moving with a speed of light:

v=c and m

_{v}takes a form of 0/0. By applying a limits we get a definite mass.

As far as real mass of electron is concerned its the rest mass. That is one single electron which is at rest. v=0

Thanks & Regards

Aziz Alam

IIT Roorkee

askIITians.

7 years ago

Mass of thoton depends upon the frame of refernce from which you are observing the photon. If your frame of reference is at rest with respect to the photon, then mass is zero.