Question

An open pipe is in resonance in 2^nd 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 n^th  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  n^th  harmonic λ = 4l/n where n is an odd number.