# Summarizing Photon Momentum

## Summary

• Photons have momentum, given by $$p=\cfrac{h}{\lambda }$$, where $$\lambda$$ is the photon wavelength.
• Photon energy and momentum are related by $$p=\cfrac{E}{c}$$, where $$E=\text{hf}=\text{hc}/\lambda$$ for a photon.

## Glossary

### photon momentum

the amount of momentum a photon has, calculated by $$p=\cfrac{h}{\lambda }=\cfrac{E}{c}$$

### Compton effect

the phenomenon whereby x rays scattered from materials have decreased energy