Question

A crest of a water wave travels 80 cm in 4 s. If
the distance between 2 successive crests is
4 mm, what is the frequency of the wave

Answer 1

First we need to find the distance travelled by the wave in 1 second.
i.e. 80 cm/4sec= 20 cm.
we know that frequency is number of waves per second.
so the frequency = Distance travelled by 1 wave/ distance between two waves
but here the units are not same so we must convert the cm to mm (for ease of calculation.
=> distance travelled by 1 wave = 20*10= 200 mm ( 1cm=10mm)
=> frequency = 200/4 = 50 waves per second