Previous Year Question

Albert Einstein was awarded the 1921 Nobel Prize in Physics. The official Nobel citation recognized his contributions to theoretical physics and especially his discovery of the law of the photoelectric effect.

In the Photoelectric Effect, light of sufficient frequency falling on a metal surface causes the emission of electrons. These emitted electrons are called photoelectrons.

In 1905, Einstein explained the phenomenon by proposing that light energy is carried in discrete packets called quanta/photons.

The energy of a photon is—

E = hν

where h = Planck constant and ν = frequency of light.

If the energy of the photon is below the work function of the metal, an electron cannot be emitted. Thus, the photoelectric effect provided important evidence for the quantum/particle nature of light.

It should be remembered that although Einstein is extremely famous for his Theory of Relativity, the Nobel Prize was not awarded to him for relativity.

Another useful fact is that this was the 1921 Nobel Prize, but Einstein actually received it in 1922, because the award had been reserved for one year.