Ocean surface waves produced by a distant storm travel into a coastal region where the water depth decreases abruptly at a sandbar. In deep water (medium 1) the waves move at 16ms−1 and have a wavelength of 22m. Upon crossing onto the sandbar (medium 2), their speed drops to 12ms−1 while the frequency set by the storm remains unchanged.
(a) Calculate the new wavelength of the waves in medium 2.
(b) Determine the ratio λ2/λ1, where λ1 is the deep-water wavelength and λ2 is the wavelength over the sandbar. Interpret the meaning of this ratio in the context of wave behaviour at the boundary.
(c) A floating marker is anchored just beyond the sandbar in medium 2. How many crests pass the marker in 5.0min? Show your reasoning.