Question

The number of possible natural oscillations of air column in a pipe closed at one end of length 85 cm whose frequencies lie below 1250 Hz are: (velocity of sound $=340m{s}^{-1}$)

• A. 4
• B. 5
• C. 7
• D. 6

Answer 1

The correct option is D 6

Fundamental frequency of a closed organ pipe is $f_1=\frac{V}{4l}=\frac{340}{4\times 0.85}=100Hz$
The natural frequencies of the organ pipe will be f = 100 Hz, 300 Hz, 500 Hz, 700 Hz, 1100 Hz which are below 1250 Hz.