CBSE 2022 · Region 1 · Set 1 · Q9 · 3 marks
Photoelectrons are emitted from a metal surface when illuminated with UV light of wavelength $\displaystyle 330$ nm. The minimum amount of energy required to emit the electrons from the surface is $\displaystyle 3.5 \times 10^{-19} \mathrm{~J}$. Calculate :(i)the energy of the incident radiation, and(ii)the kinetic energy of the photoelectron.
Photoelectrons are emitted from a metal surface when illuminated with UV light of wavelength $\displaystyle 330$ nm. The minimum amount of energy required to emit the electrons from the surface is $\displaystyle 3.5 \times 10^{-19} \mathrm{~J}$. Calculate :
(i)
the energy of the incident radiation, and
(ii)
the kinetic energy of the photoelectron.
Marking-scheme solution
(i)
ii)i) Energy of incident radiation
$$\begin{aligned}
& E=h v=h \frac{c}{\lambda}
& =\frac{$\displaystyle 6.63$ \times $\displaystyle 10$^{-$\displaystyle 34$} \times $\displaystyle 3$ \times $\displaystyle 10$^{$\displaystyle 8$}}{$\displaystyle 330$ \times $\displaystyle 10$^{-$\displaystyle 9$}}
& =$\displaystyle 6.027$ \times $\displaystyle 10$^{-$\displaystyle 19$} \mathrm{~J}
\end{aligned}
$$ii) Kinetic energy of photoelectron
$$\begin{aligned}
\text { K.E. } & =E-\phi_{$\displaystyle 0$}
& =\left($\displaystyle 6$ \cdot $\displaystyle 027$ \times $\displaystyle 10$^{-$\displaystyle 19$}-$\displaystyle 3$ \cdot $\displaystyle 5$ \times $\displaystyle 10$^{-$\displaystyle 19$}\right) \mathrm{J}
& =$\displaystyle 2$ \cdot $\displaystyle 527$ \times $\displaystyle 10$^{-$\displaystyle 19$} \mathrm{~J}
\end{aligned}
Dual Nature of Radiation and MatterEinstein’s Photoelectric Equation: Energy Quantum of RadiationApplyshort_answermedium
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CBSE Class 12 Physics past-paper question from the 2022board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.