Re: Stern-Gerlach Experiment2

On 2005-05-28, Ali <ph_question@xxxxxxxxx> wrote:
> Dear Members,
>
> In Late Sakurai's " Modern Quantum Mechanics", in the description of
> Stern-Gerlach experiment, you read "Because the atom as a whole is very
> HEAVY, we expect that the CLASSICAL CONCEPT of trajectory can be
> legitimately applied, ... " (p.3) what is the relevance of "heaviness
> of atom" to classical concept of trajectory?
> regards,

Since the atom is (microscopically) heavy it has (microscopically) large
momentum. Using the de Broglie relation between the momentum and the
characteristic wavelength, lambda = h/p, we see that the atoms
characteristic wavelength is very small.

Think about wave and ray optics. Ray geometric optics approximates well
the propagation of short wavelength E&M radiation (say light). But the
ray approximation fails for large wavelengths (say radio waves).
Similar reasoning applies to the wave description of the atom. Here the
ray approximation corresponds to the approximation that classical
trajectories are well defined and correspond closely to the trajectory
of the atom's wavepacket.

Hope this helps.

Igor

.

Relevant Pages

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