22.1.5—A photon has momentum and that the momentum is given by p = E / c

For a photon, momentum magnitude p=E/c=h/λ. Photons carry momentum despite having zero rest mass.

Use photon energy from frequency or wavelength, then divide by c; momentum direction follows propagation direction.

Shorter-wavelength photons have greater momentum because p=h/λ.

Zero rest mass does not mean zero momentum or zero pressure when photons are absorbed or reflected.