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JEE Main 2025 January Physics: Atoms & Nuclei – Previous Year Questions

All 8 questions asked from Atoms & Nuclei in JEE Main 2025 January Physics (22, 23, 24, 28 and 29 January, all shifts). This chapter is about 3.2% of the 250 Physics questions in the session: 8 single-correct (MCQ) and 0 numerical-value questions. Select an answer to attempt each question, and open “View solution” under it.

8questions
8MCQ
0numerical
3.2%of Physics paper

Topics asked in this chapter

  • Bohr Model & Atomic Spectra – 5 questions
  • Nuclei & Radioactivity – 3 questions

Bohr Model & Atomic Spectra

Q122 Jan 2025 · Shift 1MCQ
An electron in the ground state of the hydrogen atom has the orbital radius of $5.3\times10^{-11}$ m while that for the electron in third excited state is $8.48\times10^{-10}$ m. The ratio of the de Broglie wavelengths of electron in the ground state to that in the excited state is
  1. A
    9
  2. B
    4
  3. C
    16
  4. D
    3
Q222 Jan 2025 · Shift 2MCQ
An electron projected perpendicular to a uniform magnetic field $B$ moves in a circle. If Bohr's quantization is applicable, then the radius of the electronic orbit in the first excited state is :
  1. A
    $\sqrt{\dfrac{h}{2\pi eB}}$
  2. B
    $\sqrt{\dfrac{h}{\pi eB}}$
  3. C
    $\sqrt{\dfrac{2h}{\pi eB}}$
  4. D
    $\sqrt{\dfrac{4h}{\pi eB}}$
Q324 Jan 2025 · Shift 1MCQ
During the transition of electron from state A to state C of a Bohr atom, the wavelength of emitted radiation is 2000 Å{} and it becomes 6000 Å{} when the electron jumps from state B to state C. Then the wavelength of the radiation emitted during the transition of electrons from state A to state B is
  1. A
    6000 Å
  2. B
    2000 Å
  3. C
    4000 Å
  4. D
    3000 Å
Q428 Jan 2025 · Shift 2MCQ
The frequency of revolution of the electron in Bohr's orbit varies with $n$, the principal quantum number as
  1. A
    $\dfrac1n$
  2. B
    $\dfrac1{n^2}$
  3. C
    $\dfrac1{n^4}$
  4. D
    $\dfrac1{n^3}$
Q529 Jan 2025 · Shift 2MCQ
The number of spectral lines emitted by atomic hydrogen that is in the 4th energy level, is
  1. A
    3
  2. B
    6
  3. C
    0
  4. D
    1

Nuclei & Radioactivity

Q623 Jan 2025 · Shift 1MCQ
A radioactive nucleus $n_2$ has 3 times the decay constant as compared to the decay constant of another radioactive nucleus $n_1$. If initial number of both nuclei are the same, what is the ratio of number of nuclei of $n_2$ to the number of nuclei of $n_1$, after one half-life of $n_1$ ?
  1. A
    8
  2. B
    4
  3. C
    1/8
  4. D
    1/4
Q723 Jan 2025 · Shift 2MCQ
Given below are two statements. One is labelled as Assertion (A) and the other is labelled as Reason (R).
Assertion (A) : The binding energy per nucleon is found to be practically independent of the atomic number A, for nuclei with mass numbers between 30 and 170.
Reason (R) : Nuclear force is long range.
In the light of the above statements, choose the correct answer from the options given below :
  1. A
    (A) is true but (R) is false
  2. B
    (A) is false but (R) is true
  3. C
    Both (A) and (R) are true and (R) is the correct explanation of (A)
  4. D
    Both (A) and (R) are true but (R) is NOT the correct explanation of (A)
Q828 Jan 2025 · Shift 1MCQ
Choose the correct nuclear process from the below options [p: proton, n: neutron, $e^-$: electron, $e^+$: positron, $\nu$: neutrino, $\bar\nu$: antineutrino]
  1. A
    $n\to p+e^-+\bar\nu$
  2. B
    $n\to p+e^++\nu$
  3. C
    $n\to p+e^++\bar\nu$
  4. D
    $n\to p+e^-+\nu$
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