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IB · E · multiple choice

Nuclear and quantum physics · Question 6

Nuclear and quantum physics · Original GioPhysics question with a detailed, mark-by-mark answer guide.

Demand
demanding
Marks
1
Topics
1
Answer
Complete
A photoelectric cell connected to a microammeter and a d.c. supplyevacuated tubemetal surfacecollectormonochromatic lightphotoelectronsAmicroammeterd.c. supply
Fig. 6.1A photoelectric cell drawn as an evacuated tube. Inside it a flat metal plate stands on the left and a smaller collecting electrode on the right. A beam of monochromatic light enters through the top of the tube and falls on the face of the plate that faces the collector, and an arrow across the vacuum shows photoelectrons travelling from the plate to the collector. Outside the tube the plate is connected through a microammeter and along a wire to a d.c. supply, the positive terminal of which is the one joined back to the collector.
multiple choice1 mark

In a photoelectric experiment, the intensity of the incident light is increased while its frequency is held constant. What happens to the maximum kinetic energy of the emitted photoelectrons and to the photocurrent?

  1. A

    both increase

  2. B

    maximum kinetic energy unchanged, photocurrent increases

  3. C

    maximum kinetic energy increases, photocurrent unchanged

  4. D

    both unchanged

Ready to self-mark?Reveal the detailed answer guide
Answer overviewCorrect answer: B — maximum kinetic energy unchanged, photocurrent increases
01

Answer and reasoning

1 mark
How to approach it

Predict from the governing principle before looking for a matching option. Then reject alternatives by checking direction, units, limiting behaviour or the physical meaning of each statement.

  1. 1

    The correct choice is B: maximum kinetic energy unchanged, photocurrent increases

  2. 2

    A is what the classical wave model predicts and is precisely the prediction the photoelectric effect refutes. Each photon carries hf regardless of intensity, so the maximum kinetic energy depends only on frequency; more intense light means more photons, hence more electrons per second.

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