What Happens When the Electron in a Hydrogen Atom Flips $\alpha$

question 9

Multiple Choice

What happens when the electron in a hydrogen atom flips its direction of spin from parallel to antiparallel to that of the proton?

• A) Nothing. This event is a forbidden transition that never occurs.
• B) The atom emits a photon of 656.3-nm wavelength (H _\(\alpha\) ) in the red region of the spectrum.
• C) The atom emits a photon of 21-cm wavelength in the radio region of the spectrum.
• D) The atom emits a photon of 121.5-nm wavelength (L _\(\alpha\) ) in the UV region of the spectrum.

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