Planck constant
The Planck constant, or Planck's constant, is a fundamental physical constant denoted h, and is of fundamental importance in quantum mechanics. A photon's energy is equal to its frequency multiplied by the Planck constant. Due to mass–energy equivalence, the Planck constant also relates mass to frequency. Wikipedia
Symbol: symbol h britannica.com
6.62607015×10⁻³⁴ J·s
E = energy
h = Planck's constant
f = frequency