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Question
The drawing shows a ship 800 m from a cliff. A gun is fixed on the ship. After 5 seconds the people at the front of the ship hear the sound of the gun again.
(a) What is the name of this effect ?
(b) What happens to the sound at the cliff ?
(c) How far does the sound travel in 5 seconds ?
(d) Calculate the speed of sound.
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Solution
(a)The name of this effect is echo.
(b) Sound gets reflected back after reflecting from the cliff.
(c) Distance covered by sound wave in 5 s can be calculated as follows:
Incident sound travels distance (dI) = 800 m
Sound after reflection travels (dR) = 800 m
Total distance travelled by sound
= dI + dR
= (800 + 800) m
= 1600 m
(d) We have to calculate the speed of sound.
Given: Distance of cliff d = 800 m
Time taken to listen to the echo t = 5 s
So , time taken to reach the cliff `(t_1) = 5/2` s
So , speed of sound is
= `d/t_1`
= `(800 xx 2)/5` m/s
= 320 m/s
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