Question

The work function $\varphi$ of some metals is listed below. The number of metals which will show photoelectric effect when light of 300 $nm$ wavelength falls on the metal is

$\begin{array}{cccccccccc}\text{metal}& Li& Na& K& Mg& Cu& Ag& Fe& Pt& W\\ \varphi \left(eV\right)& 2.4& 2.3& 2.2& 3.7& 4.8& 4.3& 4.7& 6.3& 4.75\end{array}$

• A. b
• B. d
• C. c
• D. a

Answer 1

The correct option is B d

Energy of incident photon should be higher than work function to show photoelectric effect.
$\text{Energy of photon}=\frac{6.62\times {10}^{-34}\times 3\times {10}^8}{300\times {10}^{-19}\times 1.6\times {10}^{-19}}=4.14eV$