Question

Light wavelength $300nm$ in incident on a photosensitive surface. The stopping potential for emitted photoelectrons is $2.5V$. The wavelength of incident light is reduced to $150nm$. The stopping potential of emitted photoelectrons is

• A. A little more than $5V$
• B. A little less than $5V$
• C. Exactly $5V$
• D. Exactly $2.5V$

Answer 1

The correct option is A A little more than $5V$

We have
$\frac{2hc}{\lambda }=\varphi +eV$
and $\Rightarrow \frac{hc}{\lambda }=e(V^{\prime }-V_s)$
or $V^{\prime }=2V_s+\frac{\varphi }{e}$
or $V^{\prime }>5V$