Question

A source emits 2000Hz sound waves. At a distance of 300m from the source, a device is installed that records the arrival of waves through the air and sends them back through a straight metal wire. The length of these waves on the wire is 17m. What is the round trip time of the waves, in seconds?
Given: speed of sound in the air equal to 300m / s.

Answer 1

$t=t_1+t_2$

in the air

$t_1=\frac{300}{300}=1s$

on the wire

$t_2=\frac{300}{v}$ , $v=\lambda\cdot \nu=17\cdot2000=34000m/s$

$t_2=\frac{300}{v}=\frac{300}{34000}\approx0.01s$

the round trip time of the waves

$t=1+0.01=1.01 s$.