How Can Photons Have Momentum Without Mass?

[logearav]

Homework Statement

Photon don't have mass. But they possesses momentum.

Homework Equations

The Attempt at a Solution

Momentum is product of mass and velocity. Then how photons which don't have mass can have momentum?

 

[gneill]

Momentum is a product of mass and velocity only for things that have rest mass. For things without rest mass (like photons) another expression holds.
$$p = \frac{h \nu}{c} = \frac{h}{\lambda}$$

 

[logearav]

Thanks gneill for your clarification

 

[ehild]

The momentum of the photon can be written also as p=mc, where m=E/c². (And E=hν)

ehild