55 Hi all, Hello, Racking my brains over this : If I have two semi-infinite strings (made of same material) - which are connected by a massless spring, and now I send a longitudinal wave along one string. Will the spring just pass on the wave to the other string or will it serve to reflect some of it back ? If it does reflect some of it back, what would be the boundary conditions that you will have to impose ? Is it just that the E * du/dx which is the stress in the two strings, should be equal to k*(u1 - u2) where u1 and u2 are the displacements of the two strings at the interface between the string and the spring ? So I will just have: E * du1 /dx = -k * (u1 - u2) E * du2 /dx = k * (u1 - u2) One of the right hand sides is of opposite sign as the direction of force is opposite. Not able to show energy conservation with this. Perhaps I am using the wrong boundary conditions ? Thanks! Thanks!