Question 107 of 200
In photoelectric effect an em-wave is incident on a metal surface and electrons are ejected from the surface. If the work function of the metal is 2.14 eV and stopping potential is 2 V , what is the wavelength of the em-wave ?
(Given hc where h is the Planck's constant and c is the speed of light in vaccum.)
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Answer: (A) 300 nm
\begin{aligned}
& \phi=2.14 \\
& V_S=2 \mathrm{~V}
\end{aligned}$
Using photoelectric equation.
$\begin{aligned}
& \frac{h c}{\lambda}=2.14+2=4.14 \mathrm{eV} \\
& \lambda=\frac{1242}{4.14}=300 \mathrm{~nm}
\end{aligned}