CBSE Class 10 Science 2025 Solved Paper All Sets

Question : 20 of 20

Marks: +1, -0

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

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

Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A).
Both Assertion (A) and Reason (R) are true and Reason (R) is not the correct explanation of Assertion (A).
Assertion (A) is true but Reason (R) is false.
Assertion (A) is false but Reason (R) is true.

Solution:

The assertion states that when ciliary muscles contract, the eye lens becomes thin. This is incorrect. When the ciliary muscles contract, they release tension on the zonules (ligaments) that hold the lens in place, allowing the lens to become thicker, which increases its power to focus on nearby objects.

The reason states that ciliary muscles control the power of the eye lens, which is true, as they adjust the shape of the lens for focusing. Therefore, the assertion is false, but the reason is true.

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