Question

A metal of work function 4 eV is exposed to a radiation of wavelength $140\times {10}^{-9}m$.Then the stopping potential developed by it is:($h=6.63\times {10}^{-34}Js$ and $c=3\times {10}^8$ m/s)

• A. 6.42 V
• B. 2.94 V
• C. 4.86 V
• D. 3.2 V

Answer 1

The correct option is C 4.86 V

Stopping potential $=\frac{(\frac{hc}{\lambda }-\varphi )}{e}$
$=\frac{(\frac{1240}{140}-4)}{e}=4.86V$