If the speed of sound in air is 344 m/s at 22° C, and the minimum time interval between sound and echo is 0.1 s for a distinct echo, what is the distance the sound should travel from source to reflecting surface and then back to ear?

Correct option is B

The correct answer is option (b) 34.4 m

Explanation

To hear an echo distinctly, there must be a minimum time gap of 0.1 seconds between the original sound and its echo. The speed of sound is given as 344 m/s, and the sound travels from the source to the reflecting surface and then back. So, total distance:

$$\text{Distance}=\text{Speed}\times \text{Time}=344\times 0.1=34.4\text{m}$$

This is the total distance sound travels (to and fro). Hence, the correct answer is 34.4 meters.

Information Booster

• Minimum time gap to hear an echo = 0.1 s

• Speed of sound at 22°C = 344 m/s

• Echo distance = Speed × Time

• Total distance = 34.4 m, so the reflecting surface must be at least 17.2 m away

• Echoes are used in sonar, navigation, and acoustic measurements