# Planck constant

The Planck constant, sometimes called Planck's constant, is an important number in quantum physics. It is named after the physicist Max Planck. It was first used as a way to link the amount of energy a photon carries with the frequency of its electromagnetic wave. This idea can be written in an equation like this $E=H \times F$ where E stands for energy, H is the Planck constant and F is the frequency.