Question

Explain experimentally observed facts of the photoelectric effect with the help of Einstein’s explanation.

Answer 1

Explanation for the photoelectric effect:
The experimentally observed facts of the photoelectric effect can be explained with the help of Einstein’s photoelectric equation.

1. As each incident photon liberates one electron, then the increase of intensity of the light (the number of photons per unit area per unit time) increases the number of electrons emitted thereby increasing the photocurrent. The same has been experimentally observed.

2. From K_max = hv – Φ₀, it is evident that Kmax is proportional to the frequency of the light and is independent of the intensity of the light.

3. As given in Einstein’s photoelectric equation, there must be minimum energy (equal to the work function of the metal) for incident photons to liberate electrons from the metal surface. Below which, emission of electrons is not possible. Correspondingly, there exists a minimum frequency called threshold frequency below which there is no photoelectric emission.

4. According to the quantum concept, the transfer of photon energy to the electrons is instantaneous so that there is no time lag between the incidence of photons and the ejection of electrons.