A boy stands facing a high wall at a distance of 85 m from it and then blows a whistle. Calculate the time interval when he hears an echo (Speed of sound = 340 m $s^{-1}$).

To hear an echo, the sound must travel from the boy to the wall and reflect back, covering a total distance of twice the distance to the wall. This total distance is 85 m multiplied by 2, which equals 170 m. Using the formula time equals distance divided by speed, the time interval is 170 m divided by 340 m/s, resulting in 0.5 s.

• Thanks
• Wrong explanation