Too few examples to explain "The principles of quantum mechanics" by dirac. Hi! I studied my first course of quantum physics without a technical formalism (I'm studying physics engineering). I find some hindrances in paragraph 20. It says (I'm translating from Italian): After a few lines, he says that we can formally write [itex]|P>=\psi(\xi)[/itex], where [itex]\psi(\xi)[/itex] is the wave function. What I cannot understand is how to transpose these symbols in effective calculations. For example, if [itex]|P>[/itex] represent the superposition of the first two states of a particle (say an electron) in an infinite well, what is [itex]\psi(\xi)[/itex]? How can I find it?