In the hydrogen atom, I believe most people are familiar with the following three equations:(adsbygoogle = window.adsbygoogle || []).push({});

L^2 (psi) = l*(l+1)*hbar^2*(psi)

Lz (psi) = ml*hbar*(psi)

H (psi) = -1/n^2*junk*(psi)

where L^2, Lz, and H are the linear operators for total angular momentum squared, angular momentum about the z-axis, and energy. I'm comfortable with eigenvalues, eigenvectors, etc.The thing I don't understand, however, is what Lz really is.Since our choice of axes is completely arbitrary, I could have just as easily chosen Lx to be Lz. But of course, if I know Lz, I can not possibly know anything about Lx (other than, perhaps, its maximum value).

I gues what I'm asking is the following: is Lz just a way to say, that if we were to measure the angular momentum of an electron about a certain axis (which we'll call z) it can only have values of ml*hbar, and once we know what Lz is, we can't possibly know anything about Lx and Ly?

I'd really appreciate it if somebody could straighten this out for me.

**Physics Forums | Science Articles, Homework Help, Discussion**

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# What's the deal with Lz?

**Physics Forums | Science Articles, Homework Help, Discussion**