The question reads: "Water waves in the deep part of a ripple tank have a wavelength of 5.2cm. They approach the boundary where the shallow part begins with an angle of 25degrees between the waves and the boundary, but after they have crossed the boundary, this angle has dropped to 17degrees. What is their new wavelength" I just have no idea where to start. Could someone please help me or atleast give me a hint to how I should start this question? I'm so lost.