What change,if any,would you expect in the characteristics of musical sound when we increase $(i)$ its frequency and (ii) its amplitude?

$A$ ship sends out ultrasound waves that are detected after $4 \, s$ upon reflection from the seabed. If the speed of ultrasound through seawater is $1550 \, m \, s^{-1}$,find the distance of the seabed from the ship. (in $, m$)

What is Galton's whistle? To what use can it be put?

$(a)$ Why are sound waves called mechanical waves? List two practical applications of reflection of these waves.
$(b)$ $A$ stone is dropped from the top of a tower $125 \ m$ high into a pond of water at the base of the tower. When is the splash heard at the top? $(g = 10 \ m s^{-2}$ and speed of sound $= 340 \ m s^{-1})$

$A$ 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.

The given graph shows the displacement versus time relation for a disturbance travelling with a velocity of $1500\, m \,s^{-1}$. Calculate the wavelength of the disturbance.