15 May, 2026

Measuring Light Energy

The energy of a light

The energy of a light can be calculated using either formula:

  • E = h · f
  • E = p · c

There are two different equations because one considers the frequency of the wave, the other views the momentum of a particular.

Both equations consistently describe the same photon energy, just using different variables. They’re equivalent because photons are a special case of energy relating to a massless wave of light.