# Two stream of photons, possessing energies equal to twice and ten times the work function of metal are incident on the

Question:

Two stream of photons, possessing energies equal to twice and ten times the work function of metal are incident on the

metal surface successively. The value of ratio of maximum velocities of the photoelectrons emitted in the two respective

cases is $\mathrm{x}: \mathrm{y}$. The value of $\mathrm{x}$ is

Solution:

(1)

Forphotoelectric effectk. $\mathrm{E}_{\max }=\mathrm{E}-\phi$

$\mathrm{E}_{1}=2 \phi_{r} \quad \mathrm{k}_{1}=\phi$

$\mathrm{E}_{2}=10 \phi_{r} \quad \mathrm{k}_{2}=9 \phi$

$\therefore V \propto \sqrt{k} \quad\left(k=\frac{1}{2} m v^{2}\right)$

$\frac{v_{1}}{v_{2}}=\sqrt{\frac{1}{9}} \Rightarrow \frac{1}{3}=\frac{x}{y}$

$\mathrm{x}=1$