# How did Stern-Gerlach experiment change the concept of space quantization and electron spin?

I got confused by a question which is : "How did Stern-Gerlach experiment change the concept of space quantization and electron spin?" Its the question asked in our previous year examination. And I cannot make sense of it. In almost all of books its written that Stern-Gerlach experiment proved the concept of space quantization and electron spin.

1. I have read about the experiment, and also about its history, and at that time Stern and Gerlach didn't know about the concept of spin.

The magnetic moment they measured of silver atoms was not due to orbital angular momentum but due to spin angular momentum.

So how can it change the concept of spin? Does the question want to ask how the stern-gerlach experiment would have changed the concept of spin if both experimenters knew something about the spin. Since Uhlenbeck and Goudsmit proposed somewhat classical concept of spin so if the experiment would have been performed after Uhlenbeck's hypothesis then the classical concept would have been changed to quantum one.

1. And also it proved the concept of space quantization which was proposed by Sommerfeld :

The plane in which the orbit could be located in a magnetic field could have only certain definite orientations in space.

It proved the concept so why its asked that it changed the concept of space quantization?, What the question actually means?

• What do you mean by "space quantization?" This is not standard terminology. – Ben Crowell Apr 1 '16 at 16:02
• I think this could potentially be a good question, but right now it's too unclear what exactly you're asking. – Danu Apr 1 '16 at 17:27
• @Danu l I edited the question, I hope it will clear somewhat what I want to ask. – shivani Apr 4 '16 at 8:23

• 1. According to Sommerfeld theory L = 1 and there was no spin. He had proposed three quantum numbers n,k,m. n=k=1 (for circular orbit n=k) so m = + and - 1 (two orientations, m=0 state was rejected) So the experiment was right but the theory was wrong. 2. According to new quantum theory L = 0 but without spin there should not be any splitting, again wrong theory or incomplete theory. 3. After Uhlenbeck's hypothesis L=0 and $S= + or - 1/2$ so it predicted the splitting. – shivani Apr 4 '16 at 8:50