An experiment is being set up that requires echoes to arrive at least 0.2 s. Class 9

An experiment is being set up that requires echoes to arrive at least 0.2 s. Class 9

Question 1.

An experiment is being set up that requires echoes to arrive at least 0.2 s after the emission of sound. What minimum distance should a reflecting surface be placed at? Assume the speed of sound to be 343 m s^-1. (Page 201) Class 9

Answer:

Sound must travel to the surface and back in 0.2 s. Total distance = speed × time = 343 × 0.2 = 68.6 m Minimum distance of reflecting surface = 68.6 / 2 = 34.3 m

Question 2.

Sound travels much farther in water than light, and thus, is used for various underwater applications. A sonar signal sent to find the depth of ocean takes 4 s to return. What is the depth of the ocean at that location if the speed of sound in seawater is 1500 m s^-1? (Page 203) Class 9

Answer:

Total time = 4 s; time to reach the ocean floor = 4/2 = 2 s

Depth = speed x time = 1500 × 2 = 3000 m