A pipe open at both ends has a fundamental frequency fin 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:

Calculation:
For a pipe of length L open at both ends, the fundamental frequency (f) in air is given by the equation:

f = v/λ = (v / 2L)

⇒ λ =2L

Now, when the pipe is dipped vertically in water and half of it is submerged, the length of the air column is halved. 

⇒ L' = L/2 

⇒ λ' =4L' = 2L 

Hence, f' = v / λ' = v / 2L = f 

Correct Answer: Option 2 - f