MCQEasy1 mark
20
Select the correct option for each of the following questions A boy standing in front of a wall produces two whistles per second. He notices that the sound of his whistling coincides with the echo. The echo is heard only once when whistling is stopped. Calculate the distance between the boy and the wall. (The speed of sound in air = 320 m/s)
In which of the following timings of reflection of the whistle, the echo cannot be heard? (a) 0.05 s (b) 0.12 s (c) 0.2 s (d) 0.11 s
Topic: Echo and the time of reflection
Previous-year question practice database
Try it
Pick an option and check your answer. The full worked answer is below either way.
Answer
Exam answer
(a) 0.05 s.
Explanation
A distinct echo needs a delay of about 0.1 s or more.
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