# Quantum Mechanics: Probability of the result h-bar/2 if Sy is measured

1. Feb 25, 2013

### bbnl1990

1. The problem statement, all variables and given/known data

http://dl.dropbox.com/u/24280471/Question.PNG [Broken]

2. Relevant equations

Isn't the probability of measuring h-bar/2 the same as the probability of finding the particle in the state ψ+? Since Syψ+ = (h-bar/2)Syψ+.

3. The attempt at a solution

(Sorry, don't know how to use LaTex.)
http://dl.dropbox.com/u/24280471/Attempt.PNG [Broken]

Last edited by a moderator: May 6, 2017
2. Feb 25, 2013

### TSny

Re: Quantum Mechanics: Probability of the result h-bar/2 if Sy is meas

Yes, your solution is correct. The answer in the problem statement is incorrect. They should have left out the matrix Sy in the calculation of the probability. Note that the probability must be a dimensionless number, but they are getting something that has the dimensions h2.

3. Feb 26, 2013

### bbnl1990

Re: Quantum Mechanics: Probability of the result h-bar/2 if Sy is meas