Q.
A closed organ pipe has length ' λ '. The air in it is vibrating in 3rd overtone with maximum amplitude ' a '. The amplitude at a distance of λ/7 from closed end of the pipe.
The figure shows variation of displacement of particles in a closed organ pipe for 3rd overtone.
For third overtone l=47λ​
or λ=74l​
or 4λ​=7l​
Hence the amplitude at P at a distance 7l​
from closed end is 'a′ because there is an antinode at that point.