Question

If in a photoelectric cell, the wavelength of incident light is changed from $4000$ $\dot{A}$ to $3000$ $\dot{A}$ then change in stopping potential will be :

• A. $0.66V$
• B. $1.03V$
• C. $0.33V$
• D. $0.49V$

Answer 1

The correct option is B $1.03V$

Wavelength is changed from $4000\stackrel{0}{A}$ to $3000\stackrel{0}{A}$

$\frac{h_c}{{\lambda }_1}={KE}_{\left(max\right)}+W_0$

$\frac{h_c}{{\lambda }_2}={KE}_{{max}_{\left(2\right)}}+W_0$

$\frac{h_c}{{\lambda }_1}-\frac{h_c}{{\lambda }_2}={KE}_{{max}_{\left(1\right)}}-{KC}_{{max}_{\left(1\right)}}$

$(\frac{h_c}{{\lambda }_1}-\frac{h_c}{{\lambda }_2})\times \frac{1}{e}=V_s$

$V_s=\frac{6.62\times {10}^{-34}\times 3\times {10}^8}{1.6\times {10}^{-19}}(\frac{1}{4000}-\frac{1}{3000})$

$V_s=1.03V$