Question

An open pipe is in resonance in 2nd harmonic with frequency f1 . Now one end of the tube is closed and frequency is increased to f2 such that the resonance again occurs in nth harmonic. Choose the correct option

(a) n= 3,f2 = 3/4f1

(b) n= 3,f2 = 5/4f1

(a) n = 5,f2 = 3/4f1

(d) n = 5, f2 = 5/4 f1

Answer 1

Correct option (d) n = 5, f2 = 5/4 f1

Explanation:

Initially, the pipe is open at both ends.

For second harmonic, λ = l

∴ Frequency f1 = v/λ = v/l

Finally, the pipe is closed at one end.

For nth harmonic λ = 4l/n where n is an odd number.