CBSE 2023 · Region 2 · Set 2 · Q34 · 4 marks
Figure shows the variation of photoelectric current measured in a photo cell circuit as a function of the potential difference between the plates of the photo cell when light beams $\displaystyle \mathrm{A}, \mathrm{B}, \mathrm{C}$ and D of different wavelengths are incident on the photo cell. Examine the given figure and answer the following questions:
Potential Difference(i)Which light beam has the highest frequency and why ?(ii)Which light beam has the longest wavelength and why?(iii)Which light beam ejects photoelectrons with maximum momentum and why?What is the effect on threshold frequency and stopping potential on increasing the frequency of incident beam of light ? Justify your answer.
Figure shows the variation of photoelectric current measured in a photo cell circuit as a function of the potential difference between the plates of the photo cell when light beams $\displaystyle \mathrm{A}, \mathrm{B}, \mathrm{C}$ and D of different wavelengths are incident on the photo cell. Examine the given figure and answer the following questions:
Potential Difference
(i)
Which light beam has the highest frequency and why ?
(ii)
Which light beam has the longest wavelength and why?
(iii)
Which light beam ejects photoelectrons with maximum momentum and why?
What is the effect on threshold frequency and stopping potential on increasing the frequency of incident beam of light ? Justify your answer.
Marking-scheme solution
(iii) Identification of beam ejecting photoelectrons with maximum momentum and reason OR
(b) Effect on threshold frequency and stopping potential on the increasing frequencv and iustification - $\displaystyle 1$+$\displaystyle 1$
(i) The light beam B because it requires maximum retarding potential to reduce the photoelectric current to zero.
(ii) The light beam C because it requires minimum retarding potential to reduce photoelectric current to zero.
(iii) The light beam B ejects photoelectrons with maximum momentum. because highest frequency light beam ejects photoelectrons with highest kinetic energy and hence highest momentum.
OR
There is no effect on threshold frequency since it is characteristic of the metal.
With increase in freqquency of incidents beam of light , stopping potential increases because to stop the photoelectrons of higher kinetic energy, larger retarding potential is required.\[e V_{0}=h\left(v-v_{0}\right)
\]Dual Nature of Radiation and MatterEinstein’s Photoelectric Equation: Energy Quantum of RadiationAnalysecase_studymedium
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CBSE Class 12 Physics past-paper question from the 2023board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.