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
- ABoth Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A)
- BBoth Assertion (A) and Reason (R) are true but Reason (R) is not the correct explanation of Assertion (A)
- CAssertion (A) is true but Reason (R) is false
- 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