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IGCSE · 5 · multiple choice

Nuclear physics · Question 2

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

Demand
recall
Marks
1
Topics
1
Answer
Complete
Source, absorber and Geiger–Müller tube in line on a benchsourceradiationabsorber(paper or 5 mm aluminium)Geiger–Müller tubecounter
Fig. 2.1A radioactive source in a holder stands on the bench facing a Geiger–Müller tube that is joined by a lead to a counter. Between them an absorber is held upright in the path of the radiation: either a sheet of paper or a 5 mm sheet of aluminium. The source, the absorber and the window of the tube all lie on the same horizontal line, and the distance between the source and the tube is not changed when the absorber is put in place.
multiple choice1 mark

A radioactive source is placed near a detector. A sheet of paper does not reduce the count rate, but a 5 mm sheet of aluminium reduces it almost to background. What does the source emit?

  1. A

    α-particles only

  2. B

    β-particles only

  3. C

    γ-rays only

  4. D

    α-particles and γ-rays

Ready to self-mark?Reveal the detailed answer guide
Answer overviewCorrect answer: B — β-particles only
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: β-particles only

  2. 2

    The paper result rules out alpha, and the aluminium result rules out gamma. Both pieces of evidence have to be used, which is what makes this a two-step item rather than recall.

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