Why is the upper magnet in the Stern-Gerlach experiment wedge-shaped?

[ehrenfest]

Homework Statement

http://en.wikipedia.org/wiki/Stern-Gerlach
In the Stern-Gerlach experiment, is there a reason why the upper magnet is wedge-shaped and not flat?

Homework Equations

The Attempt at a Solution

 

[ehrenfest]

OK. Maybe that is a silly question. Now that I think about it, the wedge-shape of the upper magnet is the entire point of the experiment because it creates the inhomogenous magnetic field.

 

[Doc Al]

Exactly!

 

[HallsofIvy]

But why, exactly, was it posted under "Calculus" rather than physics?

 

[Doc Al]

Good point! I didn't even notice that. (I'll move it.)