Quantum Physics

Photons

Light is quantised into packets called photons, each with energy: $$E = hf = \frac{hc}{\lambda}$$ where $h$ = Planck's constant ($6.63\times10^{-34}$ J s). The electronvolt (eV) is a convenient energy unit: $1\text{ eV}=1.6\times10^{-19}$ J.