Question

There are four metals with following work functions.
If all of them are irradiated with the radiation of frequency $5\times {10}^{14}\text{Hz}$

Metal	Work functions $\left(\text{eV}\right)$
$A$	$2.30$
$B$	$2.75$
$C$	$4.25$
$D$	$4.70$

Which of the four may show photoelectric effect?

• A. Only $A$
• B. Only $B$ & $C$
• C. Only $A$ & $C$
• D. None of them

Answer 1

The correct option is D None of them

Here the Energy of incident radiation is,
$E=h\nu$
$E=6.63\times {10}^{-34}\times 5\times {10}^{14}$
$\therefore E=3.315\times {10}^{-19}\text{J}=2.07\text{eV}$

Here, the energy of incident radiation is lass than the work function of all of the given metals. So, none of the given metals will show emission of photoelectrons.

Hence, $\left(D\right)$ is the correct answer.

Why this question? Concept : If $E<{\varphi }_0$, no photoelectric emission will happen.