A pipe of length `85cm` is closed from one end. Find the number of possible natural oscillations of air column in the pipe whose frequencies lie below `1250 Hz`. The velocity of sound in air is `34m//s`.

Options

A. `12`
B. `8`
C. `6`
D. `4`

Answer

C

Explanation

For closed organ pipe `f = ((2n + 1)v)/(4l), (n = 0,1,2"……..")`
`((2n + 1)v)/(4l) lt 1250`
`(2n + 1) lt 1250 xx (4 xx 0.85)/(340)`
`(2n + 1) lt 12.5`
`2n lt 11.50`
`n lt 5.25`
So `n = 0, 1, 2, 3"………"5`
So we have `6` possibileties