Question

Assertion (A): For hearing a distinct echo, the minimum distance of the obstacle from the source of sound should be 17.2 m.

Reason (R): This distance changes with change of temperature.

Options

• If both Assertion and Reason are true and the Reason is correct explanation of the Assertion.

• If both Assertion and Reason are true, but Reason is not correct explanation of the Assertion.

• If Assertion is true, but the Reason is false.

• If Assertion is false, but the Reason is true.

Answer 1

If both Assertion and Reason are true, but Reason is not correct explanation of the Assertion.

Explanation:

Assertion (A) is true. For a distinct echo, the reflected sound should return after at least \(0.1\,\text{s}\). At ordinary temperature, this gives a minimum distance of about 17.2 m.

Reason (R) is true. The speed of sound changes with temperature, so the minimum distance required for a distinct echo also changes.

However, the Reason explains why the minimum distance may vary, not why it is specifically \(17.2\,\text{m}\).

Therefore, both A and R are true, but R is not the correct explanation of A.