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Chronos000
Apr18-11, 01:58 PM
1. The problem statement, all variables and given/known data

given a wavefuntion \Psi = (1/sqrt50) (3\mu1 + 5\mu2 - 4\mu3)

what is the expectation value of the total energy?


My thoughts were to calculate <\Psi|\hat{}H|\Psi>

but the previous part to the question asks for the probability of each outcome(which I know how to find). So is there a way to do this using the probabilities?

kloptok
Apr18-11, 02:59 PM
For a discrete probability distribution f(x_i) [x (and thus f) takes only discrete values], the expectation value of a quantity x is

<x>= \sum^N_i x_i f(x_i) ,

where x takes on values x_1, x_2, \ldots , x_N

For a continous probability distribution g(x) [where g and x are continous], the expectation value of x is the limit of the sum, namely the integral

<x>= \int^{x_{max}}_{x_{min}} x g(x) .

So if you know the probability distribution (which it seems like you do) the rest is basic maths.

Chronos000
Apr19-11, 01:10 PM
so are you saying that the answer is just ET = 9/50 E1 + 25/50 E2 + 16/50 E3 ?

ideasrule
Apr19-11, 01:40 PM
Yes.