Quantum Physics

Light behaves as both a wave and a stream of particles called photons — the foundation of quantum physics.

Photon energy

A photon's energy depends only on frequency: $$E = hf = \frac{hc}{\lambda}$$ where $h = 6.63 \times 10^{-34}$ J s (Planck's constant) and $c = 3.0 \times 10^{8}$ m s⁻¹.

Worked example. A photon of frequency $5.0 \times 10^{14}$ Hz has energy $E = hf = (6.63\times10^{-34})(5.0\times10^{14}) = 3.3 \times 10^{-19}$