Dear All,

I was reading the concept of stationary waves in composite string ABC made up of joining two strings AB AND BC with different mass per unit length and a joint at 'B'.the two ends of the composite string are clamped at 'A' and 'C' and a transverse wave is set up by an external source at one of the clamp say clamp 'A'.it was written in the book that stationary wave will set up in the composite string ABC at a particular frequency of external source with joint 'B' as a node.following are my doubts
1)the stationary wave in AB must be due to incident wave and reflected wave at junction B but at junction 'B' there is some reflection and some transmission(so that stationary wave in B can also be set up).due to partial reflection the amplitude of incident wave and reflected wave must be different so a perfect stationary wave is not possible in string AB.however wave in string BC is perfectly stationary(assuming no energy loss at clamp C).is my reasoning correct in this sense?
2)Why there is a node at junction?does this always happen in composite string that joint is a node?
3)the stationary wave in string AB and BC will have different amplitude because the amplitude of reflected and transmitted wave is not same?