Question

Monochromatic photons of energy $3.3eV$ are incident on a photo sensitive surface of work function $2.4eV$.

Maximum velocity of photoelectron is:

• A. $5.65\times {10}^{5}m/s$
• B. $6.65\times {10}^{6}m/s$
• C. $10.65\times {10}^{5}m/s$
• D. $2.65\times {10}^{5}m/s$

Answer 1

The correct option is A $5.65\times {10}^{5}m/s$

Given,

$\varphi =2.4eV$
$E=3.3eV$
And,
$E-\varphi =K{E}_{max}=\frac{1}{2}m\times v_{max}^2$

$v_{max}=\sqrt{\frac{0.9\times 1.6\times {10}^{-19}\times 2}{9\times {10}^{-31}}}$

$v_{max}=\sqrt{\frac{288\times {10}^{-10}}{9}}$

$v_{max}=\sqrt{32\times {10}^{-10}}$

$v_{max}=5.65\times {10}^{-5}$

Hence option $\text{A}$ is correct.