Question

For a certain organ pipe, three successive resonance frequencies are observed at $425\text{Hz}$, $595\text{Hz}$ and $765\text{Hz}$ respectively. The fundamental frequency of the pipe is -
$[$speed of sound in air $=340\text{m/s}]$

• A. $25\text{Hz}$
• B. $70\text{Hz}$
• C. $85\text{Hz}$
• D. $45\text{Hz}$

Answer 1

The correct option is C $85\text{Hz}$

Resonance frequencies refer to the frequencies at which standing waves are formed.
For the frequencies $425\text{Hz}$, $595\text{Hz}$ and $765\text{Hz}$,
$HCF$ is $85\text{Hz}$
Hence, fundamental frequency is $85\text{Hz}$.