Question 108 of 200
A light source of wavelength illuminates a metal surface and electrons are ejected with maximum kinetic energy of 2 eV . If the same surface is illuminated by a light source of wavelength , then the maximum kinetic energy of ejected electrons will be (The work function of metal is 1 eV )
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Answer: (D) 5 eV
Einstein's photoelectric equation
$\begin{aligned}
& \mathrm{KE}=\frac{h c}{\lambda}=\phi_0 \\
& 2 \mathrm{eV}=\frac{h c}{\lambda}-1 \mathrm{eV} \\
& \frac{h c}{\lambda}=3 \mathrm{eV} \\
& \mathrm{KE}^{\prime}=\frac{h c}{(\lambda / 2)}-\phi_0=6 \mathrm{eV}-1 \mathrm{eV}
\end{aligned}$
$\begin{aligned}
& \mathrm{KE}=\frac{h c}{\lambda}=\phi_0 \\
& 2 \mathrm{eV}=\frac{h c}{\lambda}-1 \mathrm{eV} \\
& \frac{h c}{\lambda}=3 \mathrm{eV} \\
& \mathrm{KE}^{\prime}=\frac{h c}{(\lambda / 2)}-\phi_0=6 \mathrm{eV}-1 \mathrm{eV}
\end{aligned}$