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NEETPhysicsWaves and Sound

Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A): If an open organ pipe is dipped vertically in water to exactly half of its physical length, its fundamental frequency will decrease when end correction is considered. Reason (R): The acoustic length of the resulting closed pipe is exactly half of the acoustic length of the original open pipe. In th

Options

  1. ABoth Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A)
  2. BBoth Assertion (A) and Reason (R) are true but Reason (R) is not the correct explanation of Assertion (A)
  3. CAssertion (A) is true but Reason (R) is false
  4. DAssertion (A) is false but Reason (R) is true

Correct answer

D. Assertion (A) is false but Reason (R) is true

Step-by-step solution

For an open pipe of physical length L and radius r , the end correction is e at both ends. The acoustic length is L_ eq = L + 2e . The fundamental frequency is f = v 2(L + 2e) . When dipped in water to half its length, it becomes a closed pipe of physical length L/2 . The end correction e applies only to the upper open end. The new acoustic length is L'_ eq = L 2 + e = L + 2e 2 . This makes the Reason (R) true. The new fundamental frequency is f' = v 4L'_ eq = v 4 ( L + 2e 2 ) = v 2(L + 2e) = f . The fundamental fr

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