Physics Van 3-site Navigational Menu

Physics Van Navigational Menu

Q & A: Momentum and energy of photons (and other particles)

Learn more physics!

Most recent answer: 05/28/2010
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.


(published on 05/28/2010)

Follow-up on this answer.