Re: Prism Light Speed

From: phoenix (photonixx_at_go.com)
Date: 03/05/05 

Date: 5 Mar 2005 15:42:47 -0800

Brian Tung wrote:
> Paul Winalski wrote:
> > Light appears to slow down when it's not traveling in a
> > vacuum, such as in a prism, because of interaction with
> > matter, electrons in particular. The electrons in the
> > prism absorb the incoming photons and then emit new ones
> > of the same wavelength. The new ones may not be at the
> > same trajectory as the incoming ones (this is responsible
> > for reflection, refraction, and scattering), and there is
> > a small time delay between when the photon is absorbed
> > and when the new one is emitted (this is responsible for
> > the light appearing to travel at a speed lower than C).
>
> Yes, although to call it a small time delay obscures some physical
> details. Classically, light is an electromagnetic vibration, and the
> electric field of the incoming light exerts a force on the electron.
> That is to say, the acceleration of the electron is proportional to
> the electric field.
>
> However, the light produced by the electron is proportional not to
> its acceleration, but by its velocity. It therefore appears delayed
> by a quarter wavelength, even though classically, it's all happening
> together at the same time.
>
> Brian Tung <brian@isi.edu>
> The Astronomy Corner at http://astro.isi.edu/
> Unofficial C5+ Home Page at http://astro.isi.edu/c5plus/
> The PleiadAtlas Home Page at http://astro.isi.edu/pleiadatlas/
> My Own Personal FAQ (SAA) at http://astro.isi.edu/reference/faq.txt

Thanks for all the explanation.

How come violet with shorter wavelength bend more than red??

What is the clearest explanation why light bend at all when
it passes thru a medium and why is it toward a certain
direction??

My questions focus on the directions prefered by light and
the different wavelength and why exactly. Thanks.

P.

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