# Photon's mass and frequency

1. Oct 23, 2006

### lightarrow

If photons had non zero rest mass, which would be the relationship between energy and frequency?

2. Oct 23, 2006

### Staff: Mentor

It would still be E = hf, same as for other particles with nonzero rest mass, such as electrons. Likewise the momentum would still be given by $p = h / \lambda$. What would change would be the relationship between energy and momentum, which would be $E = \sqrt{(pc)^2 + (m_0 c^2)^2}$ instead of E = pc.

3. Oct 27, 2006

### lightarrow

Thank you, jtbell.