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Assertion (A): When ciliary… (Class 10 Science 2025, Q20)

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ScienceCBSE Class 10 · Board exam 2025, set 31/4/1 · 1 mark · Assertion-reason

CBSE Class 10 Science 2025: question 20

Set in the CBSE Class 10 board exam of 2025, paper 31/4/1, section A, question 20, for 1 mark. Try it first; the hints and our step-by-step solution are below.

Q20 · 1 mark · Assertion-reasonCompetency-basedControl and Coordination

Assertion (A): When ciliary muscles contract, eye lens becomes thin.

Reason (R): Ciliary muscles control the power of the eye lens.

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

Source: official question paper from cbse.gov.in (PDF). See it in the full 2025 board paper, set 31/4/1.

Hints

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

Hint 1

Think about how the eye focuses on near objects.

Hint 2

For near vision the lens gets thicker.

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. A is false: when the ciliary muscles contract, the lens becomes thicker; it becomes thin when they relax.

  2. R is true: by changing the curvature of the lens, the ciliary muscles control its power. Option (D).

    1 mark

Answer: (D) A false, R true

Where the marks are

  • A false, R true (1 mark)

Revise the chapter

Practise this chapterBoard-style questions from Control and Coordination, one at a time, marked against the answer key and marking points.Back to the full paper2025 board paper, set 31/4/1: 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.