- #1
tomwilliam2
- 117
- 2
Homework Statement
I'm trying to demonstrate that if:
$$\hat{L}_z | l, m \rangle = m \hbar | l, m \rangle$$
Then
$$\hat{L}_z^2 | l, m \rangle = m^2 \hbar^2 | l, m \rangle$$
Homework Equations
$$\hat{L}^2 = \hat{L}_x^2 + \hat{L}_y^2 + \hat{L}_z^2$$
$$\hat{L}_z = -i\hbar \left [ x \frac{\partial}{\partial y} - y \frac{\partial}{\partial x} \right ]$$
The Attempt at a Solution
I'm not really sure where to start with this. I can apply the operator ##\hat{L}_z^2## to an arbitrary function ##f(x,y)##, but that gives me:
$$\hat{L}_z^2 f(x,y) = \hbar^2\left(x^2 \frac{\partial^2}{\partial y^2} - xy \frac{\partial}{\partial y} \frac{\partial}{\partial x} -xy \frac{\partial}{\partial x} \frac{\partial}{\partial y} + y^2 \frac{\partial^2}{\partial x^2} \right)f(x,y) $$
I've no idea if this demonstrates anything at all...