Nuclear Physics

Nuclear Physics MDCAT MCQs with answers

69 past paper MCQs from Physics unit 16, Nuclear Physics, across 4 topics. They are arranged topic by topic; bigger topics show a sample here and link to their full set and to study notes. Tap “Show answer” for the correct option and a short solution.

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Composition of the Atomic Nucleus

1.The protons in the nucleus of an atom DO NOT exit due to (UHS MDCAT 2025)

  1. Electromagnetic force
  2. Gravitational Force
  3. Weak Nuclear Force
  4. Strong Nuclear Force
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Correct answer: (b) Gravitational Force

Gravitation between protons is far too feeble to matter; it is the strong nuclear force that holds them.

2.Mass number A refers to _____ (KMU MDCAT 2024)

  1. Number of electrons
  2. Number of nucleons
  3. Number of neutrons
  4. Number of protons
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Correct answer: (b) Number of nucleons

The mass number counts the protons and neutrons together, that is the nucleons.

3.For two down quarks total charge is: (PMC MDCAT 2022)

  1. -2/3 e
  2. -2 e
  3. -1 e
  4. -1/2 e
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Correct answer: (a) -2/3 e

A down quark carries $-\tfrac13e$, so two of them carry $-\tfrac23e$.

All 13 Composition of the Atomic Nucleus MCQs → Composition of the Atomic Nucleus notes →

Spontaneous and Random Nuclear Decay

4.It has been observed that thorium $^{234}_{90}\mathrm{Th}$ is transformed into protactinium $^{234}_{91}\mathrm{Pa}$ after the emission of a ______ particle. (MDCAT 2022)

  1. alpha
  2. beta
  3. gamma
  4. alpha and gamma together
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Correct answer: (b) beta

The mass number is unchanged and the atomic number rises by one, which is beta-minus decay.

5.Which of the following has the maximum ionizing power? (UHS MDCAT 2017)

  1. $\alpha$
  2. $\beta$
  3. $\gamma$
  4. neutron
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Correct answer: (a) $\alpha$

The alpha particle is the heaviest and carries two units of charge, so it ionizes most strongly and is stopped soonest.

6.Stability of radioactivity element is determined by: (NUMS MDCAT 2025)

  1. Decay constant
  2. Rate of the radioactive decay
  3. Time of decay
  4. Number of radioactive nuclei
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Correct answer: (a) Decay constant

The decay constant is the probability of decay per second, so the smaller it is the more stable the nuclide.

All 19 Spontaneous and Random Nuclear Decay MCQs → Spontaneous and Random Nuclear Decay notes →

Half-Life and Rate of Decay

7.The half-life of strontium is 8.70 hours. Its decay constant is: (MDCAT 2022)

  1. $0.000022\ \mathrm{s^{-1}}$
  2. $45000\ \mathrm{s^{-1}}$
  3. $0.0022\ \mathrm{s^{-1}}$
  4. $0.22\ \mathrm{s^{-1}}$
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Correct answer: (a) $0.000022\ \mathrm{s^{-1}}$

$\lambda=0.693/T_{1/2}=0.693/(8.70\times3600)=2.2\times10^{-5}\ \mathrm{s^{-1}}$.

8.The unit of the decay constant is: (MDCAT 2024)

  1. m
  2. s
  3. $\mathrm{s^{-1}}$
  4. mm
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Correct answer: (c) $\mathrm{s^{-1}}$

The decay constant is the fraction decaying per unit time, so it is measured per second.

9.If we have $N_0$ atoms of a radioactive element, then after a period of $n$ half-lives the number of atoms left behind is: (MDCAT 2024)

  1. $2^{n}N_0$
  2. $(1/2)^{n}N_0$
  3. $(N_0)^{n}$
  4. $N_0/n$
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Correct answer: (b) $(1/2)^{n}N_0$

Each half-life halves the number, so $n$ of them leave $N_0/2^{n}$.

All 19 Half-Life and Rate of Decay MCQs → Half-Life and Rate of Decay notes →

Biological and Medical Uses of Radiation

10.Which of the following is NOT a somatic biological effect of radiation? (MDCAT 2024)

  1. skin burn
  2. loss of hair
  3. induction of cancer
  4. gene mutation
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Correct answer: (d) gene mutation

A mutation of the genes is a genetic effect, carried to the offspring; the others appear in the body of the exposed person.

11.Which of the following is NOT the Somatic biological effect of radiation? (UHS MDCAT 2024)

  1. Skin burn
  2. Loss of hair
  3. Induction of cancer
  4. Genes mutation
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Correct answer: (d) Genes mutation

A somatic effect appears in the person irradiated; a mutation in the germ cells is a genetic effect.

12.Gamma ray camera can observe radiations from the ____ that are concentrated in the organs (KMU MDCAT 2024)

  1. Atoms
  2. Isotopes
  3. Nucleons
  4. Neutrons
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Correct answer: (b) Isotopes

A gamma camera images the radioisotope that has gathered in the organ under study.

All 18 Biological and Medical Uses of Radiation MCQs → Biological and Medical Uses of Radiation notes →

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