CBSE 2025 · Region 7 · Set 3 · Q24 · 3 marks
Answer the following, giving reasons :(a)The maximum kinetic energy of the photoelectrons is independent of the intensity of incident radiation.(b)Photoelectric current increases with the increase in the intensity of the incident radiation.(c)The stopping potential $\displaystyle \mathrm{V}_{0}$ varies linearly with the frequency $\displaystyle v$ of the incident radiation for a given photosensitive surface.
Answer the following, giving reasons :
(a)
The maximum kinetic energy of the photoelectrons is independent of the intensity of incident radiation.
(b)
Photoelectric current increases with the increase in the intensity of the incident radiation.
(c)
The stopping potential $\displaystyle \mathrm{V}_{0}$ varies linearly with the frequency $\displaystyle v$ of the incident radiation for a given photosensitive surface.
Marking-scheme solution
Reason for
(a)
Independence of maximum kinetic energy of photoelectrons & intensity of incident radiation $\displaystyle 1$
(b)
Increase in photoelectric current with increase in intensity of incident radiation $\displaystyle 1$
(c)
Linear variation in stopping potential with frequency of incident radiation $\displaystyle 1$
(a)
With the variation in the intensity of incident radiations, there is a change in the number of photons not on the energies of the photons so the maximum kinetic energy of photoelectrons remains same.
(b)
With the increase in intensity of incident radiation number of photons increases as a result photoelectric current increase.
(c)
With the increase in frequency of incident radiation , the maximum kinetic energy of photoelectrons increases. Hence higher value of stopping potential (retarding potential) is required.
Alternatively:
\[K_{\max }=e \mathrm{~V}_{\mathrm{o}}=\mathrm{h} \nu-\mathrm{h} \nu_{\mathrm{o}}
\]
Dual Nature of Radiation and MatterEinstein’s Photoelectric Equation: Energy Quantum of RadiationUnderstandshort_answermedium
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CBSE Class 12 Physics past-paper question from the 2025board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.