If an explosion takes place at the bottom of a lake,what type of shock waves will be produced in the water?

Define echo. Establish a mathematical relation between speed of sound, distance of reflecting body from source of sound, and time for echo.

Sound travels in air if

How does the sound produced by a musical instrument reach your ears? Astronauts need radio transmitters to talk to each other on the moon. Why?

$A$ body vibrating with a time period of $5 \times 10^{-3} \text{ s}$ produces a wave travelling in a medium with a velocity of $1450 \text{ m s}^{-1}$. Calculate its wavelength and the frequency of vibration of the body.

State whether the following statement is true or false: Sound and light travel in a medium in the form of crests and troughs and rarefactions and compressions respectively.