The echo of the sound of a boy standing in front of a mountain is heard after 0.2 s. What is the distance of the
mountain from the boy when speed of the sound is 342 m/s?

Correct option is A

The Correct answer is (a) 34.2 m
The time for the echo to return is 0.2 seconds, but this time is for the sound to travel to the mountain and back. Therefore, the actual time taken to travel to the mountain is half of 0.2 seconds, which is 0.1 seconds.
The formula for distance is:
Distance=Speed×Time
Substituting the given values:
Distance=342 m/s×0.1 seconds=34.2 meters
Thus, the distance of the mountain from the boy is 34.2 meters.
Information Booster:
· Echo: An echo is a reflection of sound that arrives at the listener after a delay.
· Speed of Sound: The speed of sound in air is approximately 342 m/s at room temperature, but it can vary slightly based on temperature and air conditions.
· Time Taken for Echo: The total time taken for an echo includes both the forward and return journey of the sound wave.
· Distance Calculation: Since the echo travels to the mountain and back, the time to calculate the distance to the mountain is halved.
· Applications of Echo: Echoes are used in sonar technology, echolocation, and even medical ultrasound imaging.