MDCAT Physics chapter 16: Physics · Nuclear physics MCQs with answers

By Team Megalecture · Updated 4 Nov 2026

20 exam-style questions on Physics · 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.

20 questions · 2 topics · 10 per test

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What chapter 16 covers

Ten Physics · 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. Harmful effects of radiation that appear in the children of an exposed person, because of damage to reproductive cells, are called

  1. A
    genetic effects
  2. B
    somatic effects
  3. C
    thermal effects
  4. D
    chemical effects
Show answer

Answer: A. Genetic effects arise when radiation damages the DNA of reproductive cells, so the harm shows up in later generations. Somatic effects, such as radiation burns, cataracts or cancer, appear in the exposed person.

2. In a fission reaction the total mass decreases by 0.20 u. Taking 1 u = 931 MeV, the energy released is about

  1. A
    931 MeV
  2. B
    186 MeV
  3. C
    18.6 MeV
  4. D
    4655 MeV
Show answer

Answer: B. E = 0.20 × 931 ≈ 186 MeV, close to the typical 200 MeV released per fission. Dividing 931 by 0.20 instead of multiplying gives 4655 MeV.

3. The SI unit of absorbed dose, equal to one joule of radiation energy absorbed per kilogram of the absorber, is the

  1. A
    sievert
  2. B
    becquerel
  3. C
    gray
  4. D
    curie
Show answer

Answer: C. 1 Gy = 1 J kg−1. The sievert is the unit of equivalent dose (absorbed dose × RBE), and the becquerel and the curie are units of activity.

4. The mass defect of a 42He nucleus is 0.030 u. Taking 1 u = 931 MeV, its binding energy per nucleon is about

  1. A
    28 MeV
  2. B
    7.0 MeV
  3. C
    14 MeV
  4. D
    112 MeV
Show answer

Answer: B. Binding energy = 0.030 × 931 ≈ 28 MeV, shared among 4 nucleons: 28/4 = 7.0 MeV per nucleon. 28 MeV is the total binding energy, and 14 MeV divides by the 2 protons only.

5. A 73Li nucleus has a mass of 7.0144 u. Taking the mass of a proton as 1.0073 u and of a neutron as 1.0087 u, its mass defect is

  1. A
    0.0423 u
  2. B
    0.0409 u
  3. C
    0.0367 u
  4. D
    0.0465 u
Show answer

Answer: A. The nucleus has 3 protons and 4 neutrons: Δm = 3 × 1.0073 + 4 × 1.0087 − 7.0144 = 3.0219 + 4.0348 − 7.0144 = 0.0423 u. Swapping the numbers of protons and neutrons gives 0.0409 u.

6. Judged by binding energy per nucleon, which of these nuclei is the most stable?

  1. A
    238U
  2. B
    4He
  3. C
    2H
  4. D
    56Fe
Show answer

Answer: D. The binding energy per nucleon is highest, about 8.8 MeV, near iron-56. Uranium-238 has a larger total binding energy but only about 7.6 MeV per nucleon, helium-4 about 7.1 MeV and the deuteron only about 1.1 MeV.

7. A worker absorbs a dose of 1.0 mGy from γ-rays (RBE 1) and 0.5 mGy from α-particles (RBE 20). The total equivalent dose is

  1. A
    1.5 mSv
  2. B
    30 mSv
  3. C
    21 mSv
  4. D
    11 mSv
Show answer

Answer: D. Equivalent dose = absorbed dose × RBE for each radiation: 1.0 × 1 + 0.5 × 20 = 1 + 10 = 11 mSv. 1.5 mSv simply adds the absorbed doses, and 30 mSv applies the α-particle RBE to the whole 1.5 mGy.

8. Radioactive iodine-131 is used in medicine mainly to

  1. A
    find the age of ancient bones and wooden objects
  2. B
    sterilise surgical instruments and dressings
  3. C
    measure the thickness of metal sheets
  4. D
    diagnose and treat disorders of the thyroid gland
Show answer

Answer: D. The thyroid gland takes up iodine, so iodine-131 collects there; its radiation can be traced to study the gland or, in larger doses, used to destroy overactive tissue. Carbon-14 is used for dating, and γ-rays from cobalt-60 for sterilising.

9. After four half-lives, the fraction of the original radioactive nuclei that have decayed is

  1. A
    1/16
  2. B
    15/16
  3. C
    7/8
  4. D
    31/32
Show answer

Answer: B. The fraction left undecayed is (½)4 = 1/16, so the fraction that has decayed is 1 − 1/16 = 15/16. 1/16 is the fraction remaining, and 7/8 is the fraction decayed after only three half-lives.

10. In a fast breeder reactor, non-fissile uranium-238 is converted into the fissile fuel

  1. A
    uranium-235
  2. B
    plutonium-239
  3. C
    thorium-232
  4. D
    krypton-92
Show answer

Answer: B. Uranium-238 absorbs a neutron and, after two β− decays (through uranium-239 and neptunium-239), becomes plutonium-239, which is fissile. The reactor can produce more fissile fuel than it uses.

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Ways to practise this chapter

Physics · Nuclear physics: questions students ask

How many Physics · Nuclear physics MCQs are there?

20, each with the answer and a short explanation, across 2 topics: Nucleus and radioactivity, Nuclear energy and radiation. Every chapter test draws ten of them, so you can take it many times.

Is the MDCAT Physics chapter 16 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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