Momentum and Energy of Photons (and Other Particles)

If a photon has zero rest mass, then how it could have energy in terms of E=MC^2 (M is rest mass). If M is zero then E is also zero. Isn't it this way?
- Indrajit
New Delhi, India

You wrote down only part of the full equation.  The correct relation between energy, mass and momentum is  E² = (mc²)² + (pc)², where p is the momentum.   So for a zero rest-mass photon it becomes E =  pc.
No problem. 
Look at   for more information.

LeeH

(published on 05/28/2010)