6) A sinusoidal wave of amplitude A approaches and travels through a region of the string in which the mass per unit length changes gradually from p to p2. It can be shown that, in such a situation, there is no reflection (provided the distance over which the change occurs is large compared with the wavelength). On this assumption, show that the final amplitude A2 is given by; L A2 A1 = -(e) P2. [4]