Greetings chaps, This will probably be old hat to most of you, but I'm beginning to start Quantum mech. so that I can develop a deeper understanding of its application in Chemistry ( I'm a Chemistry undergrad -gauge my level from that if you will!) i.) First of all, would I be right in saying that an operator acts upon a function that gives us an observable, an observable being anything that can be measured i.e. the position operator acts upon a given function, f(x), and returns a position? ii.) The first part is just to make sure I ask the right question for the second part. In a text that I am following, namely 'Molecular Quantum Mechanics' by Atkins, a passage states (p.15): 'When we want to make contact between a calculation done using operators and the actual outcome of an experiment, we need to evaluate certain integrals. These integrals have the form: ∫f* Ω f δv where f* is the complex conjugate of f and Ω an operator. ' What does this part actually mean? For example does it mean that in order for our position operator to really give a position when acting upon a function we have to use the above integral to get anything meaningful? An extended question that stems from this is what does this mean when I have a non-complex function - how can I can take the complex conjugate of a function which doesn't involve any terms based on i? Thanks in advance, I know it's quite a heavy question and fairly generic. As I say I'm new to this so please, be gentle. Regards.