Lesson 6.4.3

6.4.3 Radioactivity Quiz: OCR Physics, Unit 5

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

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Lesson 6.4.3, Radioactivity: 20 multiple choice questions for the OCR Physics (H156), Unit 5: Particles and medical physics, written with Revision Ninja.

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The 20 questions

  1. What does it mean for radioactive decay to be spontaneous?

    • Predictable single decays
    • Fixed time intervals
    • No external trigger
    • Requires absorbed heat

  2. Which type of radiation is stopped by a thin sheet of paper?

    • Gamma rays
    • Beta-plus particles
    • Beta-minus particles
    • Alpha particles

  3. In beta-minus decay, a down quark transforms into which quark?

    • Up quark
    • Charm quark
    • Strange quark
    • Bottom quark

  4. What particle is emitted alongside a positron during beta-plus decay?

    • Tau neutrino
    • Electron antineutrino
    • Muon antineutrino
    • Electron neutrino

  5. Which radioactive isotope is measured to determine the age of ancient organic materials?

    • Carbon-12
    • Uranium-238
    • Carbon-14
    • Iodine-131

  6. Which equation correctly relates the decay constant lambda to the half-life t1/2?

    • lambda t1/2 = e^2
    • lambda t1/2 = ln(2)
    • lambda t1/2 = 2
    • lambda / t1/2 = ln(2)

  7. Which term describes radioactive decay having a constant decay probability per unit time?

    • Induced reaction
    • Exponential growth
    • Spontaneous nature
    • Random nature

  8. A source has 4.0 x 10^12 undecayed nuclei and decay constant 2.0 x 10^-5 s^-1. What is its activity?

    • 8.0 x 10^7 Bq
    • 8.0 x 10^17 Bq
    • 2.0 x 10^7 Bq
    • 2.0 x 10^17 Bq

  9. A sample has a half-life of 10 hours. What fraction remains undecayed after 30 hours?

    • 1/3
    • 1/4
    • 1/6
    • 1/8

  10. Which type of nuclear radiation requires several centimetres of lead to absorb most of it?

    • Beta-minus particles
    • Positrons
    • Gamma rays
    • Alpha particles

  11. When a carbon-14 nucleus undergoes beta-minus decay, what element does it become?

    • Nitrogen-14
    • Boron-14
    • Oxygen-14
    • Carbon-13

  12. A radioactive source activity drops from 800 Bq to 100 Bq in 24 minutes. What is its half-life?

    • 4 minutes
    • 6 minutes
    • 12 minutes
    • 8 minutes

  13. In spreadsheet modelling of radioactive decay, which formula represents the change in nuclei number delta N?

    • lambda N t
    • -lambda / N delta t
    • -lambda N delta t
    • lambda N / delta t

  14. What is the electric charge of an alpha particle in terms of elementary charge e?

    • 0
    • +1e
    • -1e
    • +2e

  15. An isotope has a decay constant of 0.0693 s^-1. What is its half-life?

    • 100 seconds
    • 10 seconds
    • 6.93 seconds
    • 0.1 seconds

  16. A radioactive source with decay constant 0.1 s^-1 has initial activity 100 Bq. What is A after 10 s?

    • 63.2 Bq
    • 50.0 Bq
    • 36.8 Bq
    • 10.0 Bq

  17. In beta-plus decay, an up quark transforms into which quark?

    • Top quark
    • Strange quark
    • Down quark
    • Charm quark

  18. Why is carbon-14 dating unsuitable for determining the age of objects only ten years old?

    • Negligible decay occurred
    • Carbon-14 fully decayed
    • Zero background radiation
    • Initial carbon varies

  19. In a dice simulation where landing on six means decay, what is the decay constant per roll?

    • 1/36
    • 1/6
    • 1/2
    • 5/6

  20. What is the main function of the moderator in a nuclear fission reactor?

    • Slow down neutrons
    • Stop gamma rays
    • Cool the reactor
    • Absorb neutrons

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