Question

When echo is heard?

• A. If the time interval between original sound and reflected sound is more than 1/10s.
• B. If the time interval between original sound and reflected sound is less 1/10s.
• C. If the time interval between original sound and reflected sound is less than 1/120s.
• D. If the time interval between original sound and reflected sound is 1/120s

Answer 1

The correct option is A If the time interval between original sound and reflected sound is more than 1/10s.

If the time interval between original sound and reflected sound is more than $\frac{1}{10}s$, then the original sound and the reflected sound can be clearly heard. This reflected sound is known as echo.