Raising and Lowering momentum operators

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soul
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Two equations of matrix elements of angular momentum ladder operators: <l,m1|L+|l,m2> = hbar sqrt((l-m2)(l+m2+1)) delta(m1,m2+1) and <l,m1|L-|l,m2> = hbar sqrt((l+m2)(l-m2+1)) delta(m1,m2-1).


I tried to use the eigenvalue of the operators but I couldn't get the result.
Can anyone help me to understand this relationship?

Thank you.
 
if you multiply out the brackets inside the square root, you will find that they are in fact the eigenvalues of the L+ and L- operators.

Remember that L+|l,m2> = Eigenvalue*|l,m2+1>

Once you have operated with L+ on the left hand side you can move the eigenvalue out to the front as it is just a number. You are left with:

<l,m1|l,m2+1>, which, by orthogonality, is 0 unless m1 = m2+1. This is precisely what the dirac delta functions on the right hand side represent.