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.

State whether the following statement is true or false:
The audible range of frequencies for human beings is $20 \, Hz - 20 \, kHz$.

Draw a labelled diagram of the auditory parts of the human ear and explain how the human ear works.

$(a)$ What is meant by intensity of sound?
$(b)$ Mention the conditions for an echo to be heard clearly.
$(c)$ $A$ ball is dropped into a pond from a height of $44.1 \, m$. The splash of sound is heard $3.13 \, s$ after the ball is dropped. Determine the velocity of sound in air.

Define the following terms and state their $SI$ units:
$(a)$ Wavelength $(b)$ Time period $(c)$ Amplitude.
Establish the relation $V = v \lambda$,where the symbols have their usual meanings.

$(a)$ Mention two practical applications of reflection of sound waves.
$(b)$ How is the pressure variation in a sound wave amplified in the human ear?
$(c)$ In a ripple tank,$10$ ripples are produced per second. If the distance between a trough and a neighbouring crest is $12 \, cm$,calculate the frequency,wavelength,and velocity of the wave.