If $20$ waves are produced per second,what is the frequency in hertz (in $, Hz$)?

$(a)$ $A$ 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?

The distance between two consecutive crests in a wave is known as:

What is a wave?

The stem of a tuning fork is pressed against a table top. Answer the following questions: $(i)$ Would the above action produce any audible sound? $(ii)$ Does the above action cause the table to set into vibrations? $(iii)$ If the answer above is yes,what type of vibrations are they? $(iv)$ Under what conditions does the above action lead to resonance?

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.