Question

Monochromatic light of frequency ${\nu }_1$ irradiates a photocell and the stopping potential is found to be $V_1$. What is the new stopping potential of the cell if it is irradiated by monochromatic light of frequency ${\nu }_2$?

• A. $V_1+\frac{h}{e}({\nu }_2-{\nu }_1)$
• B. $V_1-\frac{h}{e}({\nu }_2-{\nu }_1)$
• C. $V_1+\frac{h}{e}({\nu }_1+{\nu }_2)$
• D. $V_1-\frac{h}{e}({\nu }_1+{\nu }_2)$

Answer 1

The correct option is A $V_1+\frac{h}{e}({\nu }_2-{\nu }_1)$

When irradiated by light of frequency ${\nu }_1$, $W=h{\nu }_1-e{V}_1$
When irradiated by light of frequency ${\nu }_2$, $W=h{\nu }_2-e{V}_2\Rightarrow h{\nu }_2=W+e{V}_2\Rightarrow h{\nu }_2=(h{\nu }_1-e{V}_1)+e{V}_2\Rightarrow V_2=V_1+\frac{h({\nu }_2-{\nu }_1)}{e}$
Hence, the correct choice is (a).