# GRE solution still begs a question

## Homework Statement

http://whoisntdavidrinaldi.com/physics/split.png [Broken]

AxB=C

## The Attempt at a Solution

I understand that the beam splits, but why does it not split horizontally? If I hold my index finger to the page with my middle finger up then my thumb is either left or right..

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## Answers and Replies

jfizzix
Gold Member
Since the beam of hydrogen atoms electrically neutral, the Lorentz force law doesn't come explicitly into play. It is the magnetic dipole moments of the hydrogen atoms which determine which way the beam deflects.

Because the magnetic field is oriented vertically, the torque on the hydrogen atoms is such as to align their magnetic moments vertically (or at least precess about the vertical axis. However, because this magnetic field is not constant over the length of each atom, the atoms experience a net force as well, deflecting them either upward or downward depending on their magnetic moments.

Since a hydrogen atom in its ground state is equally likely to be spin-up or spin-down, we see the beam deflected into two equally intense halves.

i want to delete this post

jfizzix
Gold Member
I'm sorry if my answer was unsatisfactory, but isn't that overdoing it?

1 person
I'm sorry if my answer was unsatisfactory, but isn't that overdoing it?

No your answer was perfect, I responded but re-read your post and it answered the question I thought I had. Not knowing how to delete my post I just edited my answered follow up question to "id like to delete this post"

the answer was great, I thank you

HallsofIvy