CBSE Class 12 · 2019 · Modern PhysicsShort Answer

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(a) Define the terms (i) threshold frequency and (ii) stopping potential in the photoelectric effect. (b) Plot a graph of photocurrent versus anode potential for radiation of frequency

ν

and intensities

I_{1}

and

I_{2}

(I_{1} < I_{2})

Answer: $ν_{0}$ , $V_{0}$ defined; graph: same $V_{0}$ , $I_{2}$ higher saturation current.

Solution

(a)(i) Threshold frequency

ν_{0}

: the minimum frequency of incident radiation that can just cause photoemission from the metal.
(ii) Stopping potential

V_{0}

: the retarding anode potential at which the photocurrent becomes zero;

e V_{0} = K_{ma x}

.
(b) Since the frequency is the same, both curves have the same stopping potential

- V_{0}

; the higher intensity

I_{2}

gives the larger saturation current (see figure).

Same V_{0}; saturation current \propto intensity (I_{2} > I_{1})

CBSE Class 12 Board · 2019 · Subjective

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CBSE Class 12 · 2019 · Modern PhysicsShort Answer

Solution

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