1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Sakurai chapter 3, Problem 1.

  1. Feb 12, 2014 #1
    hello guys

    Suppose an electron is in the spin state alpha=(a,b). if s_y is measured, what is the probability of result h/2 ?


    s_y eigenvector for +h/2 is |y+>=1/sqrt(2) (1,i)) so the probabilty is (<y+|alpha>)^2 . but in the solution i attached , the solution is different ! i'm confused !



    thank you for your help
     

    Attached Files:

    • sl.jpg
      sl.jpg
      File size:
      77.5 KB
      Views:
      267
  2. jcsd
  3. Feb 12, 2014 #2
    Don't bother, your solution is correct.
     
  4. Feb 12, 2014 #3
    so the solution is incorrect ?
     
  5. Feb 12, 2014 #4
    well there's certainly something wrong when you measure a probability in terms of [itex]\hbar[/itex]2...
     
  6. Feb 12, 2014 #5

    vela

    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper
    Education Advisor

    Yes, the solution is incorrect. Whoever wrote it made the common mistake of conflating making a measurement with applying the associated operator. In other words, the "solution" calculates ##\langle +_y \lvert \hat{S}_y \rvert \alpha,\beta\rangle## for the probability amplitude while you correctly calculated ##\langle +_y \vert \alpha,\beta\rangle##.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Similar Discussions: Sakurai chapter 3, Problem 1.
Loading...