Draw a plot showing the variation of photoelectric current with collector plate potential for two different frequencies $\nu_1 > \nu_2$ of incident radiation having the same intensity. In which case will the stopping potential be higher? Justify your answer.

CBSE Class 12 · 2011 · Modern PhysicsShort Answer

Draw a plot showing the variation of photoelectric current with collector plate potential for two different frequencies

ν_{1} > ν_{2}

of incident radiation having the same intensity. In which case will the stopping potential be higher? Justify your answer.

Answer: Same saturation current; higher stopping potential for $ν_{1}$ .

Solution

Since the two beams have the same intensity, both curves reach the same saturation current, but they cut the potential axis at different stopping potentials (see figure).
From

e V_{0} = h ν - ϕ_{0}

, a higher frequency gives a larger

K_{ma x}

and hence a higher stopping potential.
Therefore the stopping potential is higher for the beam of frequency

ν_{1}

V_{0} is higher for ν_{1} (higher frequency)

CBSE Class 12 Board · 2011 · Subjective

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