An echo is returned in $6$ seconds. What is the distance of the reflecting surface from the source (in $, m$)? [Given that the speed of sound is $342 \, m s^{-1}$]

State whether the following waves are transverse or longitudinal waves :
$(i)$ light waves
$(ii)$ waves in water and
$(iii)$ sound waves.

Sound of explosions taking place on other planets is not heard by a person on the Earth. Give the reason.

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

$(a)$ $A$ particular transmitter of Aakashvani broadcasts at $420.5\, m$ wavelength. Given the speed of radio waves $3 \times 10^{8}\, m s^{-1}$. Calculate the frequency at which the radio station broadcasts its programme.
$(b)$ What is the direction of oscillations of the medium particles through which a
$(i)$ transverse wave is propagating?
$(ii)$ longitudinal wave is propagating?

If an explosion takes place at the bottom of a lake,what type of shock waves will be produced in the water?