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Question:

A pipe open at both ends has a fundamental frequency f in air. The pipe is dipped vertically in water so that half of it is in water. The fundamental frequency of the air column is now:

f

3f/4

2f

f/2

Solution:

Since the pipe is now closed on one end and also the length is halved, both factors will cancel each other and hence fundamental frequency will remain constant. In case I, λ/2=l and in II case λ/4=l/2