A light of wavelength ' $\lambda$ ' and intensity ' $I$ ' falls on photosensitive material. If '…

A light of wavelength ' $\lambda$ ' and intensity ' $I$ ' falls on photosensitive material. If ' $\mathrm{N}$ ' photo electrons are emitted, each with kinetic energy ' $E$ ', then
  1. $E \propto I, N \propto \lambda$
  2. $\mathrm{E} \propto \mathrm{I}, \mathrm{N} \propto \mathrm{I}$
  3. $\mathrm{E} \propto \mathrm{I}, \mathrm{N} \propto \frac{1}{\lambda}$
  4. $\mathrm{E} \propto \frac{1}{\lambda}, \mathrm{N} \propto \mathrm{I}$

Solution

Intensity is proportional to the number of photons, since each photon interacts with one electron, the number of electron $\mathrm{N} \propto \mathrm{I}$. Energy of photon is $\frac{h c}{\lambda}$, hence it is inversely proportional to the wavelength.

Asked in: MHT CET 2021 (24 Sep Shift 2)

Practice more Dual Nature of Matter and Radiation questions on Aicharya