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Nuclei — NEET & JEE MCQs with answers
This chapter examines nuclear structure, properties, and energy processes. It covers atomic masses, isotopes, nuclear size and density, mass–energy equivalence, binding energy, nuclear forces, radioactivity (alpha, beta, gamma decay), and nuclear energy release through fission and fusion.
Topics in this chapter
- 13.1 Introduction
- 13.2 Atomic Masses and Composition of Nucleus
- 13.3 Size of the Nucleus
- 13.4 Mass-Energy and Nuclear Binding Energy
- 13.5 Nuclear Force
- 13.6 Radioactivity
- 13.7 Nuclear Energy
Free practice questions
Taking $1\,\text{u} = 1.66\times10^{-27}$ kg, a mass of $7\,\text{u}$ equals:
- A. $1.16\times10^{-25}$ kg
- B. $1.16\times10^{-26}$ kg
- C. $1.33\times10^{-26}$ kg
- D. $1.16\times10^{-27}$ kg
Show answer
Answer: B — $ 7\times1.66\times10^{-27} = 1.16\times10^{-26}$ kg.
NCERT Class 12 Physics Ch 13 ("atomic mass unit (u), defined as 1/12th of the mass of the carbon (12C)")
If the mass number $A$ of a nucleus becomes four times its original value, its volume becomes:
- A. Sixty-four times
- B. Sixteen times
- C. Twice
- D. Four times
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Answer: D — Volume $\propto A$, so a four-fold increase in $A$ makes the volume four times larger.
NCERT Class 12 Physics Ch 13 ("of the nucleus, which is proportional to R 3 is proportional to A")
The binding energy per nucleon $E_{bn}$ is comparatively lower for:
- A. both light nuclei ($A<30$) and heavy nuclei ($A>170$)
- B. only nuclei with $A=56$
- C. no nuclei; it is the same for all
- D. only middle-mass nuclei ($30<A<170$)
Show answer
Answer: A — NCERT: '$E_{bn}$ is lower for both light nuclei ($A<30$) and heavy nuclei ($A>170$).'
NCERT Class 12 Physics Ch 13 ("Ebn is lower for both light nuclei")
The energy released in ${}^{2}_{1}\mathrm{H} + {}^{2}_{1}\mathrm{H} \rightarrow {}^{3}_{2}\mathrm{He} + n$ (reaction 13.13b) is
- A. $0.42$ MeV
- B. $3.27$ MeV
- C. $5.49$ MeV
- D. $4.03$ MeV
Show answer
Answer: B — NCERT gives $3.27$ MeV for reaction 13.13(b).
NCERT Class 12 Physics Ch 13 ("deuterons combine to form the light isotope of helium.")
Gamma-rays are electromagnetic radiation of wavelengths that are ____ those of X-rays.
- A. Longer than
- B. Equal to
- C. Unrelated to
- D. Shorter than
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Answer: D — The summary states that gamma-rays are electromagnetic radiation of wavelengths shorter than X-rays.
NCERT Class 12 Physics Ch 13 ("b-rays are electrons. g-rays are electromagnetic radiation of wavelengths")
In the NCERT analogy, if an atom is enlarged to the size of a classroom, the nucleus would be about the size of a:
- A. Pinhead
- B. Grain-less than a point
- C. Football
- D. Classroom door
Show answer
Answer: A — NCERT: if an atom is enlarged to the size of a classroom, the nucleus would be of the size of a pinhead.
NCERT Class 12 Physics Ch 13 ("would be of the size of pinhead")
Unlike Coulomb's law or Newton's law of gravitation, the nuclear force
- A. follows an inverse-square law
- B. is exactly given by Coulomb's law
- C. follows an inverse-cube law
- D. has no simple mathematical form
Show answer
Answer: D — NCERT: there is no simple mathematical form of the nuclear force, unlike Coulomb's law or Newton's law of gravitation.
NCERT Class 12 Physics Ch 13 ("simple mathematical form of the nuclear force.")
In Greek, the word 'isotope' means:
- A. the same mass
- B. the same charge
- C. the same place
- D. the same nucleus
Show answer
Answer: C — NCERT (p.307): 'In Greek, isotope means the same place, i.e. they occur in the same place in the periodic table of elements.' Isotopes in fact differ in mass, so 'the same mass' is wrong; 'the same charge' and 'the same nucleus' are not the meaning given.
NCERT Class 12 Physics · Ch 13 · 13.2 Atomic Masses and Composition of Nucleus
For a nucleus with mass number $A = 1$, the radius $R = R_0 A^{1/3}$ (with $R_0=1.2$ fm) is:
- A. $3.6$ fm
- B. $2.4$ fm
- C. $4.8$ fm
- D. $1.2$ fm
Show answer
Answer: D — $R = 1.2\times 1 = 1.2$ fm.
NCERT Class 12 Physics Ch 13 ("R = R 0 A1/3")
For the same quantity of matter, nuclear sources produce roughly how many times more energy than a chemical source?
- A. About a thousand times
- B. About the same
- C. About a million times
- D. About ten times
Show answer
Answer: C — NCERT: nuclear sources produce a million ($\sim 10^{6}$) times more energy than a chemical source per unit matter.
NCERT Class 12 Physics Ch 13 ("sources produce a million times more energy than a chemical source.")
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