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Assertion (A): In… (Class 12 Physics SQP 2026-27, Q13)

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PhysicsCBSE Class 12 · Sample paper, session 2026-27 · 1 mark · Assertion-reason

CBSE Class 12 Physics sample paper 2026-27: question 13

From the official CBSE sample question paper for 2026-27, section A, question 13, for 1 mark. Try it first; the hints and our step-by-step solution are below.

Q13 · 1 mark · Assertion-reasonCompetency-basedAtoms

Assertion (A): In Rutherford’s scattering experiment, most of the alpha particles passed through the gold foil undeflected.

Reason (R): The electrons in the atom are very light and do not affect the path of the alpha particles significantly.

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

Source: official sample paper from cbseacademic.nic.in (PDF). See it in the full Sample paper 2026-27.

Hints

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

Hint 1

Why do most alpha particles pass straight through the foil?

Hint 2

Is the lightness of electrons the main reason, or the tiny nucleus?

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. Assertion: true. Most alpha particles pass undeflected because most of the atom is empty space.

    ½ mark

  2. Reason: true, since light electrons barely deflect alpha particles. However, the empty-space explanation is the real cause, so R does not explain A. Option (B).

    ½ mark

Answer: Option (B)

Where the marks are

  • Both statements true, but R is not the correct explanation (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 paperSample paper 2026-27: 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.