A slinky lying straight on a smooth floor is given a gentle push to produce longitudinal waves along its length. The distance between the first and sixth compression measured at one instant is 75cm. A stopwatch shows that 15 compressions pass a fixed mark on the floor every second.
(i) Find the wavelength of the wave in the slinky.
(ii) Calculate the frequency of the wave.
(iii) Determine the speed of the wave along the slinky.
(iv) How many rarefactions exist between the first and sixth compression (counting both ends)?