Max Planck was a physicist who lived during the early 20th century. He concluded that the transfer of energy must work differently at the subatomic level. At the subatomic level, things are VERY small. This includes the particles that make up atoms such as electrons.
Planck suggested that energy at the subatomic level must be transferred as small “packets” instead of being transferred continuously. These packets of energy are called quanta. Quanta are said to be discrete which means that they are individual units and cannot be divided into smaller packets. When we are talking about light energy, quanta are called photons.
As the investigation into the structure of the atom continued, a constant was identified that was able to relate the energy of a photon of light to the frequency of its wave.
The frequency of a wave is equal to the number of wavelengths of the wave that pass a given point in one second. One wavelength is equal to the distance between two adjacent crests of the wave. This constant was named “Planck’s constant” in honor of Max Planck.
Planck’s constant is symbolized by the small letter “h” when it is used in equations. It is equal to 6.63 x 10-34 J•s. The letter “J” stands for the energy unit joule. The letter “s” stands for the time unit seconds.
The equation that uses Planck’s constant to relate energy and frequency is: E = hf. In this equation, “E” stands for energy, “f” stands for frequency, and “h” stands for Planck’s constant. This means that you can calculate the energy of a photon of light by multiplying its frequency by Planck’s constant.