If the velocity of sound in air is `320 m//s`, then the maximum and minimum length of a pipe closed at one end , that would produce a just audible sound would be

Options

A. `2.6 m` and `3.6 mm`
B. `4 m` and `4.2 mm`
C. `3 m and 3 mm`
D. `4 m and 4 mm`

Answer

D

Explanation

For closed organ pipe ,
`f = (v)/( 4 L) xx ( 2 n - 1)`
For minimum and maximum length of pipe the fundamental frequency of pipe must be `20 kHz and 20 Hz`, respectively .
`20 = (320)/( 4 L_(max))`
`L_(max) = 4 m`
` 20 xx 10^(3) = (320)/( 4L_(min))`
`L_(min) = 4 mm`