Question

In order to produce an echo, the minimum distance between the source of the
sound and the reflecting body should be:
A.14 m
B.16 m
C.17 m
D.20 m

Answer 1

Sound is consistently treated as a wave. The medium is whatever issue fills the volume that the sound goes through. In the viable case we are typically discussing sound waves going through air.

Complete answer:
The correct answer is C.
Henceforth, the absolute separation secured by the sound from the purpose of age to the reflecting surface and back ought to be in any event $\left( 344\text{ }m/s \right)\text{ }\times 0.1\text{ }s\text{ }=\text{ }34.4\text{ }m$. In this manner, for hearing particular echoes, the base separation of the snag from the wellspring of sound must be half of this separation.
I.e., $\dfrac{34.4}{2}\approx 17m$
As the impression of sound endures in our cerebrum for about 0.1 s, to hear an unmistakable reverberation the time span between the first solid and the reflected one must be in any event 0.1 s. In the event that we take the speed of sound to be 344 m/s at a given temperature, state at in air, sound must go to the hindrance and reach back the ear of the audience on reflection after 0.1s.
A reflection is seen when a sound reflects back to the wellspring of the sound and is heard for a second (or third, or fourth) time after some deferral.

Note: Reflection is a marvel experienced by waves. At the point when a wave goes from one medium into another, a specific level of the wave’s energy doesn't move into the subsequent medium, yet is rather convoluted.

This happens on the grounds that various mediums have an alternate impedance they force upon the wave. Impedance is a proportion of the capacity of the medium to convey the wave. It is practically similar to how simple it is for the wave to go through the medium.