A closed organ pipe has length `L`. The air in it is vibrating in thirf overtone with maximum ampulitude a . The amplitude at distance`(L)/(7)` from closed of the pipe is

Explanation

The figure shows variation of displacement of particles in a closed organ pipe for `3^(rd)` overtone.
For third overtone `l = (7lambda)/(4)` or `(4l)/(7)` or `(lambda)/(4) = (l)/(7)`

Hence the amplitude at `P` at a distance `(l)/(7)` from closed end is `'a'` because there is an antinode at that point.