Question

Write Einstein’s photoelectric equation. State clearly how this equation is obtained using the photon picture of electromagnetic radiation. 

Write the three salient features observed in photoelectric effect which can be explained using this equation.

Answer 1

Einstein photo electric equation is hv = ϕ₀ + K_max, The energy (hv) carried by a photon of frequency n is absorbed by electrons on the surface to 

(i) overcome the work function of metal ϕ_0. 

(ii) impart maximum K.E. to the emitted electron (K_max.) ∴​ hv = ϕ₀ + K_max 

Three salient features are: 

(i) Cut-off potential of the emitted electrons is proportional to v. 

(ii) Photo electric emission of electrons is possible only when v > v₀ = ϕ₀/h

(iii) Max. K.E. is independent of intensity of incident radiations.