$(i)$ Define the time period of a wave.
$(ii)$ Give the relation among speed of sound $V$,wavelength $\lambda$ and its frequency $\nu$.

For hearing the loudest ticking sound of the clock,find the angle $x$ in the figure. (in $^o$)

What is $SONAR$?

Give reasons for the following:
$(a)$ The reverberation time of a hall used for speeches should be very short.
$(b)$ $A$ vibrating body produces sound. However,no sound is heard when a simple pendulum oscillates in air.
$(c)$ Sounds of same loudness and pitch but produced by different musical instruments like a violin and flute are distinguishable.

$A$ 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 $, m$)

Draw the sound waves for a low-pitched and a high-pitched sound. Write one use of ultrasonography. Which wave property determines pitch?