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Reason (A) : In Bohr model of… (Class 12 Physics 2026, Q16)

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PhysicsCBSE Class 12 · Board exam 2026, set 55/1/1 · 1 mark · Assertion-reason

CBSE Class 12 Physics 2026: question 16

Set in the CBSE Class 12 board exam of 2026, paper 55/1/1, section A, question 16, for 1 mark. Try it first; the hints and our step-by-step solution are below.

Q16 · 1 mark · Assertion-reasonCompetency-basedAtoms

Reason (A) : In Bohr model of hydrogen atom, the energy levels are discrete and quantised.
Reason (R) : In a hydrogen atom, the electrostatic force on the electron provides the necessary centripetal force to it to revolve around the nucleus.

  1. (A)Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
  2. (B)Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).
  3. (C)Assertion (A) is true, but Reason (R) is false.
  4. (D)Both Assertion (A) and Reason (R) are false.

Source: official question paper from cbse.gov.in (PDF). See it in the full 2026 board paper, set 55/1/1.

Hints

Open one hint at a time and try again before the next.

Hint 1

Which Bohr postulate introduces n?

Hint 2

Does the force balance alone restrict orbits?

Step-by-step solution

Each step shows the marks it earns, as an examiner would award them. Checked by an independent re-solve from the question paper.

  1. Both statements are true.

  2. Quantisation of energy comes from the quantisation of angular momentum, , not from the Coulomb force supplying the centripetal force. So R does not explain A.

    1 mark

Answer: Option (B)

Where the marks are

  • Both true, but quantisation arises from the angular momentum postulate (1 mark)

Revise the chapter

Practise this chapterBoard-style questions from Atoms, one at a time, marked against the answer key and marking points.Back to the full paper2026 board paper, set 55/1/1: every question, by section.

The question is transcribed from the official paper; figures are described in words. The solution, hints and chapter tag are ours. Spotted an error? Write tosupport@questionbuddy.in.