Sound produced by a thunderstorm is heard $10 \, s$ after the lightning is seen. Calculate the approximate distance of the thunder cloud. (Given speed of sound $= 340 \, m \, s^{-1}$.) (in $, m$)

$(i)$ Even if a loud explosion were to take place at any place on the moon,it would not be heard at a nearby point. Give reason.
$(ii)$ Explain in brief the dependence of speed of sound on the nature of the material medium and temperature.
$(iii)$ Identify the two factors on which the loudness of sound depends.

$A$ sound wave with frequency higher than $20 \,kHz$ is not audible for human ear. Answer the following in respect of this statement:
$(i)$ What is the term used for such a sound?
$(ii)$ Name two organisms producing sound in this range.
$(iii)$ Write an application of such a wave.

$A$ source is producing $1500$ sound waves in $3$ seconds. If the distance covered by a compression and an adjacent rarefaction is $68 \, cm$,find $(a)$ frequency,$(b)$ wavelength,and $(c)$ velocity of the sound wave.

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.