$A$ 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 $, m$)

How do you account for the fact that two strings can be used to give notes of the same pitch and loudness but of different quality?

If the frequency of a tuning fork is $400 \, Hz$ and the speed of sound in air is $340 \, m s^{-1}$,find how far sound travels when the tuning fork makes $16$ vibrations. (in $, m$)

$(a)$ 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 $= 340 \ m s^{-1})$

$(a)$ Write two points of difference between sound wave and light wave.
$(b)$ Write an expression relating wave velocity, wavelength and frequency if speed of sound in air is $340 \, m s^{-1}$.
Calculate:
$(i)$ Wavelength when frequency $= 256 \, Hz$.
$(ii)$ Frequency when wavelength $= 0.85 \, m$.

What is a longitudinal wave?