If the echo is heard 0.5 seconds after the sound is emitted, and the speed of sound is 343 m/s, what is the distance to the reflecting surface?

If the echo is heard 0.5 seconds after the sound is emitted, and the speed of sound is 343 m/s, what is the distance to the reflecting surface?

• A. 171.5 meters
• B. 343 meters
• C. 85.75 meters
• D. 171.0 meters

Answer: (C)

Sound travels to the surface and back in the given time, so the time corresponds to a round trip. The total distance the sound covers in 0.5 s is 343 m/s × 0.5 s = 171.5 meters. That distance includes the way out and the return, so the distance to the surface is half of that: 171.5 ÷ 2 = 85.75 meters.

Sound travels to the surface and back in the given time, so the time corresponds to a round trip. The total distance the sound covers in 0.5 s is 343 m/s × 0.5 s = 171.5 meters. That distance includes the way out and the return, so the distance to the surface is half of that: 171.5 ÷ 2 = 85.75 meters.