Question

A pipe 30 cm long is open at both ends. Which harmonic mode of the pipe is resonantly excited by a 1.1 kHz source ? (Take speed of sound in air = 330 ms^–1)

• A. First
• B. Second
• C. Third
• D. Fourth

Answer 1

Answer: (A)

First

Answer 2

Fundamental frequency of open pipe

$n_{1} = \frac{v}{2l} = \frac{330}{2 \times 0.3} = 550Hz$

First harmonic = $2 \times n_{1} = 1100Hz$. = $1.1kHz$