If you want to find the energy quantum of light, you multiply the frequency of the radiation (v) by “h”. What is “h”?
The Planck constant (denoted h, also called Planck’s constant) is a physical constant that is the quantum of action, central in quantum mechanics.
The Planck constant is related to the quantization of light and matter. It can be seen as a subatomic-scale constant. In a unit system adapted to subatomic scales, the electronvolt is the appropriate unit of energy and the petahertz the appropriate unit of frequency. Atomic unit systems are based (in part) on the Planck constant.