Why will an echo not be heard when the distance between the source of sound and the reflecting surface is 10 m ?

Explanation

To determine why an echo will not be heard when the distance between the source of sound and the reflecting surface is 10 m, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Echo**: An echo is a reflection of sound that arrives at the listener after a delay. For an echo to be heard, the sound must travel to a reflecting surface and back to the listener.

2. **Time for Sound to Travel**: The human ear can perceive sound for a brief period. The sound impression lasts on the eardrum for about 1/10th of a second (0.1 seconds).

...