The threshold wavelengths for photoelectric emission from two metals $\mathrm{A}$ and $\mathrm{B}$ are $400…
The threshold wavelengths for photoelectric emission from two metals $\mathrm{A}$ and $\mathrm{B}$
are $400 \mathrm{~nm}$ and $800 \mathrm{~nm}$ respectively. The ratio of their work functions, $\phi_{A}$ to $\phi$ ?
is
$\frac{1}{2}$
4
$\frac{1}{4}$
2
Solution
work function $\phi=\frac{h c}{\lambda_{0}}$
$\therefore \frac{\phi_{B}}{\phi_{A}}=\frac{\lambda_{B}}{\lambda_{A}}=\frac{800}{400}=2$