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Assertion (A): The… (Class 12 Physics SQP 2025-26, Q14)

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PhysicsCBSE Class 12 · Sample paper, session 2025-26 · 1 mark · Assertion-reason

CBSE Class 12 Physics sample paper 2025-26: question 14

From the official CBSE sample question paper for 2025-26, section A, question 14, for 1 mark. Try it first; the hints and our step-by-step solution are below.

Q14 · 1 mark · Assertion-reasonCompetency-basedRay Optics and Optical Instruments

Assertion (A): The critical angle of light passing from glass to air is minimum for violet colour.
Reason (R): The wavelength of blue light is greater than the light of other colours.

  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 2025-26.

Hints

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

Hint 1

Relate critical angle to refractive index.

Hint 2

Which colour has the longest wavelength?

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. Since and is largest for violet, the critical angle is least for violet, so the assertion is true.

  2. Red light, not blue, has the longest wavelength in the visible range, so the reason is false. Option (C).

    1 mark

Answer: Option (C)

Where the marks are

  • Uses with maximum, and rejects R (1 mark)

Revise the chapter

Practise this chapterBoard-style questions from Ray Optics and Optical Instruments, one at a time, marked against the answer key and marking points.Back to the full paperSample paper 2025-26: 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.