22.1.3—E = hf

The energy of one photon is E=hf=hc/λ, where h is Planck’s constant, f frequency and λ wavelength.

Use frequency in hertz or wavelength in metres and check that higher frequency means higher photon energy.

Halving wavelength doubles photon energy in vacuum.

E=hf is energy per photon, not total beam energy; total energy also depends on how many photons arrive.