Wavelength is the distance between 2 crests or 2 troughs in a wave.
Period is the time taken for one wave to be completed. Frequency is the number of waves to pass a particular point in 1 second.
Period and frequency are inversely proportional
to find the speed we have to use the following equation
v = fλ
where v - speed, f - frequency and λ - wavelength
we have been given the period (T) so we have to find frequency (f)
f = 1/T
f = 1 / 20 s = 0.05 s⁻¹
v = 0.05 s⁻¹ x 200 m
v = 10 m/s
the speed of the wave is 10 m/s
