Question:

An air column in a pipe which is closed at one end will be in resonance with a vibrating tuning fork of frequency 415 Hz for various vibrating air columns. Which one of the following lengths is not in resonance ? (velocity of sound in air = 332 m/s) (Neglect end correction)

Show Hint

A closed pipe resonates at odd multiples of a quarter wavelength.
Updated On: Oct 1, 2026
  • \(20 \text{cm}\)
  • \(40 \text{cm}\)
  • \(60 \text{cm}\)
  • \(100 \text{cm}\)
Show Solution
collegedunia
Verified By Collegedunia

The Correct Option is B

Solution and Explanation

Step 1: Wavelength
\(\lambda = \frac vf = \frac{332}{415} = 0.8\ \text{m}\), so \(\frac\lambda4 = 20\ \text{cm}\).

Step 2: Condition
Resonance in a closed pipe needs \(l = (2n+1)\frac\lambda4\), so \(l = 20, 60, 100, 140\ \text{cm}\ldots\).

Step 3: Compare
\(20\), \(60\) and \(100\) cm are odd multiples of \(20\). \(40 cm\) is an even multiple, so it is not in resonance. Option (B).

Final Answer:
40 cm is not in resonance. \[ \boxed{\text{(B)}\ 40\ \text{cm}} \]
Was this answer helpful?
0
0