Question

The maximum velocity of an electron emitted by light of wavelength $\lambda$ incident on the surface of a metal of work function $\phi$ is :

• A. $\left[\frac{2( hc +\lambda \phi)}{ m \lambda}\right]^{1 / 2}$
• B. $\left[\frac{2( hc -\lambda \phi)}{ m \lambda}\right]^{1 / 2}$
• C. $\frac{2( hc -\lambda \phi)}{ m }$
• D. $\left[\frac{2( h \lambda-\phi)}{ m }\right]^{1 / 2}$

Answer 1

Answer: (B)

$\frac{ hc }{\lambda}-\phi=\frac{1}{2} mv ^{2}$
$\sqrt{2\left(\frac{ hc -\lambda \phi}{\lambda m }\right)}= V$