Question

If the velocity of sound in air is $336m/s$. The maximum length of a closed pipe that would produce a just audible sound will be :

• A. $3.2cm$
• B. $4.2m$
• C. $4.2cm$
• D. $3.2m$

Answer 1

The correct option is B $4.2m$

Velocity of sound in air $v=336m/s$

As we are quite well known that the lowest frequency of audible sound is $20Hz$. Hence maximum length of a closed pipe to produce just audible sound is given by

$l=\frac{336}{4\times v}=\frac{336}{4\times 20}$

$=4.2m$