Question

(i) Name the type of wave which are used for sound ranging.
(ii) Why are these waves mentioned in $\left(i\right)$ above, not audible to us?

Answer 1

Explanation for the part $\left(i\right)$:

1. The ultrasonic waves are used for sound ranging.
2. In sound ranging ultrasonic waves are sent to find the obstacle and then the echo of these waves are detected by the receiver.
3. The total time $\left(t\right)$ of to and fro journey of the pulse is recorded. Then the distance $\left(d\right)$ can be calculated using the relation,
   $d=\frac{vt}{2}$
   Where, $\left(d\right)$ is the distance, $\left(t\right)$ is the total time, $\left(v\right)$ is the velocity of the object.

Explanation for the part $\left(ii\right)$:

1. Ultrasonic waves are used for sound ranging because their wavelength range is $100\AA$ to $4000\AA$ and they can penetrate deep without losing intensity.
2. The ultrasonic waves are not audible to the human ear because their frequency is more than $20,000Hz$ but the audible range of the human ear is $20Hz$ to $20,000Hz$.