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Q: What is the approximate minimum distance between source and reflector for echo?
  • A. 36 m
  • B. 36 m
  • C. 17 m
  • D. 10 m
Correct Answer: Option C - Conditions for the production of an echo : (i) Sufficient distance between the source of sound and reflector will be 17.2 meter. The speed of sound in air is 344 m/s. The distance travelled by sound in 0.1 s = 344 x 0.1 = 34.4 m. So echo will be heard distinctly if the minimum distance between the source of sound and the obstacle = 34.4/2 = 17.2 m.
C. Conditions for the production of an echo : (i) Sufficient distance between the source of sound and reflector will be 17.2 meter. The speed of sound in air is 344 m/s. The distance travelled by sound in 0.1 s = 344 x 0.1 = 34.4 m. So echo will be heard distinctly if the minimum distance between the source of sound and the obstacle = 34.4/2 = 17.2 m.

Explanations:

Conditions for the production of an echo : (i) Sufficient distance between the source of sound and reflector will be 17.2 meter. The speed of sound in air is 344 m/s. The distance travelled by sound in 0.1 s = 344 x 0.1 = 34.4 m. So echo will be heard distinctly if the minimum distance between the source of sound and the obstacle = 34.4/2 = 17.2 m.