Hi. I am confused about the following problems. Any help would be appreciated. Thanks 1. I don't understand what ψ (r)= <r|ψ> means. What is the difference between the wavefunction ψ and the ket |ψ> ? 2. A similar equation is ψ (p) = <p|ψ>. Is this ket |ψ> the same as the one above or is it expressed in terms of p instead of r ? 3. Momentum p=[itex]\hbar[/itex]k ; so if k is quantised as in the infinite square well why is p not quantised ?