Question

Graph of cut-off potential $\left(V_{0}\right)$ versus frequency $\left(\right.f\left.\right)$ for same intensity of light for metal plates $A$ and $B$ are as shown in the figure below. Choose the correct statement.

• A. Work function of metal $A$ is greater than work function of metal $B$
• B. Work function of metal $A$ is less than work function of metal $B$
• C. Work function of metal $A$ is equal to work function of metal $B$
• D. Both line have same intercept

Answer 1

Answer: (B)

$hf=hf_{0}+eV_{0}$
$\therefore eV_{0}=hf-hf_{0}$
$V_{0}=\frac{h f}{e}-\frac{h f_{0}}{e}$
As $\left( \text{Intercept}\right)_{B}>\left(\text{Intercept}\right)_{A}$
$\left(\frac{h f_{0}}{e}\right)_{B}>\left(\frac{h f_{0}}{e}\right)_{A}$
$\therefore \phi_{A} < \phi_{B}$