$A$ note is a sound:

$(a)$ The sound of an explosion on the surface of a lake is heard by a boatman $100 \ m$ away and a diver $100 \ m$ below the point of explosion. Of the two persons mentioned (boatman or diver),who would hear the sound first and why?
$(b)$ Calculate the wavelength of a sound wave whose frequency is $220 \ Hz$ and speed is $440 \ m \ s^{-1}$ in a given medium.

State whether the following statement is true or false:
Light waves require no medium for their propagation.

What do you understand by the term ultrasonic vibrations?

State any two characteristics of a wave motion.

Two friends were playing on identical guitars whose strings were adjusted to give notes of the same pitch. Will the quality of the two notes be the same? Give a reason for your answer.