The echo of a gun shot is heard $8 \, s$ after the gun is fired. How far from the shooter is the surface that reflects the sound (in $, m$)? (Velocity of sound in air $= 350 \, m/s$)

$A$ nuclear bomb exploded $200 \,km$ above the surface of the moon. The sound of the explosion on the moon

Which one of the following statements is true?

$A$ plane sound wave passes from medium $1$ into medium $2$. The speed of sound in medium $1$ is $200 \, m/s$ and in medium $2$ is $100 \, m/s$. The ratio of the amplitude of the transmitted wave to that of the incident wave is:

$A$ granite rod of $60 \ cm$ length is clamped at its middle point and is set into longitudinal vibrations. The density of granite is $2.7 \times 10^3 \ kg/m^3$ and its Young's modulus is $9.27 \times 10^{10} \ Pa$. What will be the fundamental frequency of the longitudinal vibrations in $kHz$?

$A$ man standing on a cliff claps his hands and hears the echo after $1 \, s$. If the sound is reflected from another mountain and the velocity of sound in air is $340 \, m/s$,then the distance between the man and the reflection point is ..... $m$.