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Chapter 7 Practice Paper: Radioactivity and half-life — question paper

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QQ/GCSE-PHYS/CH7

GCSE (9–1) · GCSE Physics (Foundation and Higher)

Chapter 7 Practice Paper

Radioactivity and half-life

Duration: 40 minutes
Total: 30 marks
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READ THESE INSTRUCTIONS FIRST

  • Answer all questions.
  • Section A contains ten multiple-choice questions. Choose one answer, A, B, C or D, for each.
  • Section B contains structured questions. Write your answers in the spaces provided.
  • You may use a calculator.
  • The number of marks is given in brackets [ ] at the end of each question or part question.
  • The total mark for this paper is 30.

Original practice material written for the MOE GCSE Physics syllabus. It is not an official MOE or school examination paper. Chapter 7: alpha, beta and gamma radiation, nuclear equations, activity and half-life, decay graphs, background radiation, contamination vs irradiation, uses and hazards.

For Examiner’s Use
Section A/ 10
Section B/ 20
Total/ 30

Section A: Multiple-choice questions[10 marks]

Choose one answer for each question. Each question is worth 1 mark.

  1. 1

    The particle emitted when a neutron changes into a proton is

    1. Aa helium nucleus
    2. Ba fast electron
    3. Can EM wave
    4. Da neutron
    ( )
  2. 2

    The most penetrating radiation is

    1. Aalpha
    2. Bbeta
    3. Cgamma
    4. Dthey penetrate equally
    ( )
  3. 3

    When ¹⁴₆C decays by beta-minus emission, the daughter nucleus has

    1. AA = 14, Z = 7
    2. BA = 13, Z = 6
    3. CA = 14, Z = 5
    4. DA = 10, Z = 8
    ( )
  4. 4

    ²¹⁰₈₄Po alpha-decays. The daughter has mass number

    1. A214
    2. B210
    3. C208
    4. D206
    ( )
  5. 5

    A source undergoes 300 decays in one minute. Its activity is about

    1. A300 Bq
    2. B5 Bq
    3. C18 000 Bq
    4. D1 Bq
    ( )
  6. 6

    An activity of 400 Bq falls to 50 Bq. That takes

    1. A2 half-lives
    2. B4 half-lives
    3. C3 half-lives
    4. D8 half-lives
    ( )
  7. 7

    Two identical uranium atoms are watched closely. Their decay times

    1. Awill be identical
    2. Bdouble when heated
    3. Care set by their electrons
    4. Dcannot be predicted individually
    ( )
  8. 8

    A householder measures 20 s⁻¹ with no source present. This reading is best described as

    1. Aa fault in the detector
    2. Bcontamination
    3. Cbackground radiation
    4. Dirradiation of the tube
    ( )
  9. 9

    Radioactive atoms stuck on a worker’s glove are an example of

    1. Acontamination
    2. Birradiation
    3. Cbackground radiation
    4. Ddecay
    ( )
  10. 10

    A tracer isotope should have

    1. Aa half-life of decades
    2. Bno radiation at all
    3. Cstrong alpha emission
    4. Da half-life of a few hours and emit gamma
    ( )

Section B: Structured questions[20 marks]

Answer all questions in the spaces provided.

  1. 11

    A laboratory measures a source behind different absorbers with a Geiger–Müller tube. The background rate is 10 s⁻¹.

    Count rates

    Absorber between source and detectorMeasured rate / s⁻¹
    None (air only, 2 cm)310
    Sheet of paper10
    3 mm aluminium10
    1. (a)

      State which radiation the source emits, and justify your answer with the data.

      [2]
    2. (b)

      Calculate the corrected count rate with no absorber.

      [1]
    3. (c)

      The count rate in air falls to 37.5 s⁻¹ corrected when the source is moved. If the half-life is 4 days and the fall is due to decay, calculate how many days passed.

      [2]
    4. (d)

      State one limitation of the air-gap comparison.

      [1]
  2. 12

    This question is about nuclear equations and half-life.

    1. (a)

      Americium-241 (²⁴¹₉₅Am) emits an alpha particle. State the mass number and atomic number of the daughter nucleus.

      [2]
    2. (b)

      Explain why beta-minus decay increases the atomic number by one.

      [2]
    3. (c)

      A source has an activity of 1 200 Bq. Calculate its activity after 5 half-lives.

      [2]
    4. (d)

      The half-life of the source is 3 hours. Calculate how long the 5 half-lives took.

      [1]
    5. (e)

      Explain why the activity approaches zero but never reaches it.

      [2]
  3. 13

    A hospital uses technetium-99m (gamma emitter, half-life 6 hours) as a tracer for a patient’s kidneys.

    1. (a)

      Explain why a gamma emitter is chosen rather than an alpha emitter.

      [2]
    2. (b)

      Give one reason the short half-life is good for the patient after the scan is finished.

      [2]
    3. (c)

      The injected activity is 40 MBq. Calculate the activity after 18 hours.

      [1]

— End of paper —