O Level / IGCSE Physics chapter 5: Nuclear physics MCQs with answers

By Team Megalecture · Updated 4 Nov 2026

63 exam-style questions on Nuclear physics, each with the answer and a short explanation. Ten of them are below to try. The chapter test draws ten fresh questions each time and is marked the moment you finish, with your score by topic.

63 questions · 2 topics · 10 per test

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What chapter 5 covers

Ten Nuclear physics questions with answers

Try each one, then open the answer. These ten stay the same; the test draws new ones every time.

1. A nucleus of radium, 22688Ra, emits an alpha particle and becomes a nucleus of radon, Rn. What is the nuclide notation for the radon nucleus?

  1. A
    22286Rn
  2. B
    22288Rn
  3. C
    22486Rn
  4. D
    22687Rn
Show answer

Answer: A. An alpha particle is 42He, so the nucleon number falls by 4 (226 → 222) and the proton number by 2 (88 → 86).

2. A radioactive tracer is injected into a patient to check kidney function. Which isotope properties are most suitable?

  1. A
    alpha emitter, long half-life
  2. B
    gamma emitter, short half-life
  3. C
    beta emitter, very long half-life
  4. D
    alpha emitter, short half-life
Show answer

Answer: B. Gamma passes out of the body to be detected and is weakly ionising; a short half-life limits the dose after the test. Alpha inside the body would cause severe damage.

3. An excited nucleus emits gamma radiation only. What happens to the nucleus?

  1. A
    Its proton number goes up by 1
  2. B
    Its nucleon number goes down by 4
  3. C
    It becomes a nucleus of a different element
  4. D
    It loses energy but its proton number and nucleon number are unchanged
Show answer

Answer: D. Gamma radiation is electromagnetic energy with no mass and no charge, so the nucleus keeps the same numbers of protons and neutrons and simply becomes less energetic.

4. Which is the largest source of background radiation for most people?

  1. A
    nuclear power stations
  2. B
    radon gas from rocks and soil
  3. C
    medical X-rays
  4. D
    cosmic rays only
Show answer

Answer: B. Radon gas from the ground is the biggest contributor for most people, followed by rocks and buildings, food and drink, cosmic rays and medical uses.

5. Before the scattering experiment, the atom was thought to be a sphere of positive charge, with its mass spread evenly through it and electrons dotted inside. What result would this model predict?

  1. A
    almost all alpha particles bounce straight back
  2. B
    about half pass through and half bounce back
  3. C
    all alpha particles pass through with at most small deflections
  4. D
    all alpha particles are absorbed by the foil
Show answer

Answer: C. Spread-out charge and mass cannot exert a large enough force to turn an alpha particle back, so only small deflections were expected. The few large deflections seen showed the charge and mass are concentrated in a tiny nucleus.

6. A neutral atom has a nucleon number of 27 and contains 14 neutrons. How many electrons does it have?

  1. A
    13
  2. B
    14
  3. C
    27
  4. D
    41
Show answer

Answer: A. Protons = 27 − 14 = 13. A neutral atom has as many electrons as protons, so 13 electrons. 14 confuses electrons with neutrons.

7. In the nuclear model of the atom, which particles orbit the nucleus?

  1. A
    electrons
  2. B
    protons
  3. C
    neutrons
  4. D
    protons and neutrons
Show answer

Answer: A. The nucleus contains protons and neutrons; negatively charged electrons orbit around it.

8. A uranium-235 nucleus (proton number 92) absorbs one neutron and splits into barium-141 (proton number 56), krypton-92 (proton number 36) and some free neutrons. How many free neutrons are released?

  1. A
    1
  2. B
    2
  3. C
    3
  4. D
    4
Show answer

Answer: C. Nucleons before: 235 + 1 = 236. After: 141 + 92 = 233, so 236 − 233 = 3 neutrons. Forgetting the absorbed neutron gives 2.

9. What is meant by background radiation?

  1. A
    Ionising radiation that is present all the time from natural and artificial sources around us
  2. B
    Radiation given out only by nuclear power stations and medical sources
  3. C
    Radiation that has passed through a thick lead shield
  4. D
    Infrared radiation given out by all warm objects
Show answer

Answer: A. Background radiation is the low level of ionising radiation that is always present, mostly from natural sources such as radon, rocks, food and cosmic rays, with a small artificial part.

10. A technician handles a sealed radioactive source only with long-handled tongs and puts it away as soon as the experiment ends. Which safety measures do these two actions use?

  1. A
    shielding only
  2. B
    increasing distance only
  3. C
    shielding and reducing exposure time
  4. D
    increasing distance and reducing exposure time
Show answer

Answer: D. The tongs keep the source further from the hands (distance), and returning it quickly reduces the exposure time. Neither action puts anything between the source and the body, so neither is shielding.

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Ways to practise this chapter

Nuclear physics: questions students ask

How many Nuclear physics MCQs are there?

63, each with the answer and a short explanation, across 2 topics: The nuclear model of the atom, Radioactivity. Every chapter test draws ten of them, so you can take it many times.

Is the O Level / IGCSE Physics chapter 5 test free?

Yes. The test, the answers and the explanations are free and need no sign-up. Sign in only if you want your scores kept across devices.

How is the chapter test marked?

The moment you press Finish: your score, the right answer and an explanation for every question, and the ones you got wrong saved in My mistakes to retry.

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