A closed organ pipe of length `l` is vibrating in its first overtone. There is a point `Q` inside the pipe at a distance `7L//9` from the open end. The ratio of pressure amplitude at `Q` to the maximum pressure amplitude in the pipe is:

Options

A. `1:2`
B. `2:1`
C. `1:1`
D. `2:3`

Answer

A

Explanation

`DeltaPm=2DeltaP_(0) coskx` (assuming closed end as origin)
At point `Q,x=L-(7L)/9=(2L)/9`
`DeltaPm=2DeltaP_(0)cos((2pi)/(lamda)xx(2L)/9)=DeltaP_(0)`
`:.` Required ratio `=1:2`