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Physics · 2023 · 2 marks
CBSE 2023 · Region 5 · Set 1 · Q20
(a) How will the De Broglie wavelength associated with an electron be affected when the (i) velocity of the electron decreases? and (ii) accelerating…
(a)
How will the De Broglie wavelength associated with an electron be affected when the (i) velocity of the electron decreases ? and
(ii)
accelerating potential is increased ? Justify your answer.
OR
(b)
How would the stopping potential for a given photosensitive surface change if (i) the frequency of the incident radiation were increased ? and (ii) the intensity of incident radiation were decreased ? Justify your answer.
Marking-scheme solution
(a)
(i) \(\displaystyle \lambda=\mathrm{h} / \mathrm{mv}\)
With decrease in velocity, de- Broglie wavelength increases
(ii) \(\displaystyle \lambda=\frac{\mathrm{h}}{\sqrt{2 m e V}}\)
With increase in accelerating potential, de- Broglie wavelength decreases
OR
(b)
(i) With increase in frequency stopping potential will increase.
\(\displaystyle V_{0}=\frac{h}{e} \nu-\frac{\phi_{0}}{e}\)
(ii) Stopping potential remains same.
Energy of photoelectron ejected is independent of intensity of radiation
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