Question

How does the photoelectric effect support the notion of wave particle duality?

Answer 1

Photoelectric effect is a phenomenon in which when light rays fall on a metal surface results in the emission of charged particles. Before photoelectric effect was introduced, light was considered a wave because it undergoes reflection, refraction and diffraction just like a wave.

Complete step by step answer:
In the photoelectric effect when light rays are incident on the metal then the metal emits electrons from its surface which are known as photoelectrons. The number of electrons that are emitted and their kinetic energy depends on the frequency of the light rays that were incident on the metal. This whole process is termed as photoemission. Albert Einstein concluded that the photoelectric effect points to the particle nature of the light where the light is considered to be made up of particles which are called photons and have packets of energy. According to him the energy of photons is:
$E = h\nu$
Where $E$ is the energy of photon (in Joules),
$h = 6.626 \times {10^{ - 34}}Js$, which is the Planck’s constant,
And $\nu$ is the frequency of a photon (in Hertz).

The emission of electrons from the metal surface depends on this certain quantum amount of energy. If the intensity of the light rays is increased then we could have a greater number of electrons emitting from the surface of the metal but by increasing the frequency increases the average energy of each electron that is emitted. This supports the fact that light is made up of particles. Earlier the light was considered as a wave but after the photoelectric effect came into picture the light was considered to have wave particle duality.

Note: The electrons emitted by the metal when light rays are incident on it is because the electrons absorb the energy of the light rays incident on the metal surface and use it to free themselves from the surface of the metal.