A boy stands 165 m in front of a high wall and then blows a whistle. Calculate the time interval when he hears an echo. (Speed of sound = 330 m `s^(-1)`)

Explanation

To solve the problem of calculating the time interval when the boy hears the echo of the whistle he blows, we can follow these steps:

### Step 1: Understand the scenario
The boy is standing 165 meters away from a high wall. When he blows the whistle, the sound travels to the wall and then reflects back to him, creating an echo.

### Step 2: Calculate the total distance traveled by the sound
The sound travels to the wall and back to the boy. Therefore, the total distance (S) the sound travels is:
\[ S = \text{Distance to the wall} + \text{Distance back} = 165 \, \text{m} + 165 \, \text{m} = 330 \, \text{m} \]

### Step 3: Use the speed of sound
The speed of sound is given as 330 m/s.

### Step 4: Calculate the time taken for the sound to travel the total distance
We can use the formula:
\[ t = \frac{s}{v} \]
where:
- \( t \) is the time,
- \( s \) is the total distance traveled (330 m),
- \( v \) is the speed of sound (330 m/s).

Substituting the values:
\[ t = \frac{330 \, \text{m}}{330 \, \text{m/s}} \]

### Step 5: Perform the calculation
\[ t = 1 \, \text{s} \]

### Conclusion
The time interval when the boy hears the echo is **1 second**.

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