(a) What is the range of the wavelengths of light that is visible to the human eye? ( 2 ) (b) Longitudinal waves show regions of compression and rarefaction. Explain what is meant by a compression and a rarefaction in terms of the behaviour of air molecules. ( 6 ) (c) The diagram below represents a water wave. Calculate the number of wavelengths there are between X and Y. ( 4 ) (d) A signal is transmitted from a ship and an echo is received from an object below the ship 4 5 later. Calculate the distance of the object from the ship it the speed of sound in water is 1400 mls. (3)