question_answer

What is an echo? What should be the minimum distance between the source of sound and the reflector for hearing a distinct echo?

Answer:

                Echo is the phenomenon of repetition of sound due to its reflection from the surface of a large obstacle. If s be the distance between the source and reflector, \[\upsilon \] the velocity of sound and t be the total time taken by sound to reach the listener after the reflection, then \[2s=\upsilon t\] or \[s=\frac{\upsilon t}{2}=\frac{340}{2}\times \frac{1}{10}=17m.\]