Solve the question of and select the option from the choices A through D/E. Check your Answer and view the explanation.
Question: 5
To hear a clear echo, the minimum distance between the reflecting surface and the observer should be-
- 165 feet
- 165 metre
- 16.5 feet
- 16.5 metre
Show/Hide Explanation
Correct Answer: D
0
The repetition of sound produced due to the reflection from a large surface like wall, hill or mountain is called echo. Consider an observer is producing a sound and it gets reflected by an obstacle. The sound travel towards the observer and the observer hear the sound again. Let d be the distance between the observer and the obstacle, v is the sound velocity and t is the time taken by the sound to and fro motion, then the velocity of the sound is given by
V= 2d/t
Velocity of sound is given by, V = 2d/t
Where t = time taken by the sound for to and fro motion.
Substituting t = 1/10 sec, it is minimum time required to distinguish between two sounds
V = velocity of sound = 330 m/sec
at 20° C
then d=Vt/2=1/2 [330×(1/10)]
= 16.5 m