Water waves in a classroom ripple tank are produced by a vibrator that moves the water surface up and down. Successive crests are observed to be 5cm apart. During an observation interval of 2.0s a particular crest is seen to travel 0.80m along the tank.
(i) Calculate the speed of these water waves.
(ii) Determine their frequency and period.
(iii) Express the frequency in kilohertz to three significant figures.