In a closed end pipe of length `105 cm` , standing waves are set up corresponding to the third overtone . What distance from the closed end, amongst the following is a pressure node?

Options

A. `20 cm`
B. `60 cm`
C. `85 cm`
D. `45 cm`

Answer

D

Explanation

pressure node means displacement antinode

`(7 lambda) / (4) = 105 cm`
`(lambda) / (4) = 15 cm`
Displacement antinodes are a distance
`(lambda) / (4)`, `(3 lambda) / (4)`, `(5 lambda) / (4)` and `(7 lambda) / (4)` from closed end or at a
distance of `15 cm` , `45 cm`, `75 cm` , and `105 cm` .