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 `=340ms^(-1)`).
A. `4`
B. `5`
C. `7`
D. `6`

Answer 1

Correct Answer - D
For closed organ pipe possible frequency,
`f_n=(2m+1)(v)/(4l)`
for `n=0,f_0=100Hz`
`n=1,f_1=300Hz`
`n=2,f_2=500Hz`
`n=3,f_3=700Hz`
`n=4,f_4=900Hz`
`n=5,f_5=1100Hz`
`n=6,f_6=1300Hz`
Hence possible natural oscillation whose frequencies
are less than `1250 hz` will be `6(n=0,1,2,3,4,5)`