A zinc surface is exposed separately to two monochromatic radiations of equal…

PHYSICS · Subjective · A Level · Physics · Particles and radiation · Particles and radiation

Problem

A zinc surface is exposed separately to two monochromatic radiations of equal intensity but different frequencies

\nu_1

and

\nu_2

, where

\nu_1>\nu_2>\nu_0

(the threshold frequency of zinc). (i) On a single set of axes, sketch the expected photocurrent–voltage curves corresponding to the two frequencies and label them as Curve A and Curve B. (ii) Indicate on your sketch which curve corresponds to the higher frequency and explain your choice. (iii) Give a reason why the saturation currents of the two curves are practically identical, although their stopping potentials are different. (iv) If the measured stopping potentials are

2.1\,\text{V}

for

\nu_1

and

1.0\,\text{V}

for

\nu_2

, calculate the ratio

K_{\text{max},1}/K_{\text{max},2}

of the maximum kinetic energies of the emitted electrons for the two cases.

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