10/12/2025
Einstein studied how light interacts with metal and noticed something strange. Shining bright light was not always enough to release electrons. Only light with enough frequency could do it.
He suggested that light energy comes in small packets which were later called photons. Each photon carries energy based on the frequency of the light and a constant known as the Planck constant.
If a photon has enough energy it can knock a single electron out of a metal surface. If the frequency is too low no electron is released no matter how strong the light is.
This idea proved that light behaves not only like a wave but also like a particle. It helped explain results that classical physics could not understand at the time.
Einstein work on this effect later earned him the Nobel Prize. Today this discovery is used in solar panels light sensors and many modern electronic devices.