State whether the following is true or false.

For hearing distinct echoes, the minimum distance of the obstacle from the source of sound must be at least around 17m. This distance will change with the temperature of the air.

The given statement is true.

• To hear a distinct echo, the time interval between the original and reflected sound must be greater than or equal to 0.1 seconds.
• As a result, the minimum distance of the obstruction from the source of sound must be around 17 m.
• The air temperature will have an impact on this distance.
• This happens because the speed of sound changes when the temperature of air changes.
• When the temperature of air increases, the speed of sound in a medium also increases. Due to this the sound will travel faster and takes less than 0.1 s to cover the distance of 17m. Hence the echo will not be heard. As a result, the minimum distance will be greater than 17 m.
• Whereas, when the temperature decreases, the speed of sound also decreases. As a result, the minimum distance will decrease than 17 m.

Therefore, the minimum distance to a hear an echo will change with the temperature of air.