Question

The work function of a surface of a photosensitive material is $6.2eV$. The wavelength of the incident radiation for which the stopping potential is $5Vlies$ in the:

• A. ultraviolet region
• B. $X-$ray region
  
• C. infrared region
• D. none of these

Answer 1

The correct option is A ultraviolet region

$e{V}_{\circ }=h\vartheta -h{\vartheta }_{\circ }h\vartheta =\frac{hc}{\lambda }=e{V}_{\circ }+h{\vartheta }_{\circ }=5eV+6.2eV\frac{hc}{\lambda }=11.2eV\to \lambda =\frac{hc}{11.2eV}=1.104\times {10}^{-7}\therefore$

Ultraviolet region