Question

Statement 1: Ram is standing at a distance of 33 m from a wall. He claps and hears the echo of his own clap.
Statement 2: Velocity of sound in air is 330 m/s and time of persistence for hearing is $\frac{1}{10}$ of a second.

• A. Statement 1 is true and information in statement 2 is sufficient to prove it.
• B. Statement 1 is false but information in statement 2 is insufficient to prove it.
• C. Statement 1 is false and information in statement 2 is sufficient to prove it.
• D. Statement 1 is true but information in statement 2 is insufficient to prove it.

Answer 1

The correct option is A

Statement 1 is true and information in statement 2 is sufficient to prove it.

Time taken by the sound of Ram's clap to come back after reflection from the wall is the time taken for sound to travel a distance twice the distance between Ram and the wall. So, $t=\frac{(2\times 33)}{330}=\frac{1}{5}$ s. Since t is greater than the time of persistence of hearing ($\frac{1}{10}$ s), Ram will hear the echo of his clap. So, statement 1 is true and information in statement 2 is sufficient to prove it.