QM- Why is the separation constant +/-l(l+1) ?

1. Oct 24, 2011

jinksys

This isn't a HW problem, it's more of a general question. I'm reading Griffith's Intro to QM 3rd Edition. On page 134 he uses separation of variables, of which I'm familiar (but by no means an expert). Could someone explain why the separation constant in equations 4.16 and 4.17 changes sign?

The equations in question : http://imgur.com/8OKqz" [Broken]

Last edited by a moderator: May 5, 2017
2. Oct 24, 2011

vela

Staff Emeritus
If you look at the equation above those two, you see the terms sum to 0, so if one is positive, the other one is negative.

3. Oct 24, 2011

jinksys

Jeez, that should have been obvious!