Re: [Phys-l] refraction question

[Ken Fox <physicsfox23@gmail.com>]

One interesting practical experience here is as follows:
In one of those semi-circular dishes used to examine refraction, place a
diffraction grating close to the flat edge and no water. Direct a laser beam
normal to the surface and examine the resulting pattern of spots.
Add water and observe how the spots move inward exactly by the amount
predicted for lambda/n.

I think we run into problems trying to talk about the wavelength of a
photon. Light cannot be treated as a particle and a wave at the same time,
as I understand it. I know I do not know how to use photons to explain the
redirection of light when it refracts.

Ken Fox

On Fri, Apr 23, 2010 at 6:22 AM, <daryl@darylscience.com> wrote:

> Hi, Anthony. I'll take a stab at this.
>
> The photons does not change wavelength while traveling through glass or
> water. That is an analogy we use to describe the air-glass interface and
> should not be perceived as a real model. Follow one red photon. It will be
> absorbed by an electron in the first glass molecule it bangs into. This
> electron will "jump" to a higher energy state and come right back down.
> Thereby, it emits an identical red photon. However, while the photon is "in
> existence", it is traveling at 'c' through the empty space between the glass
> molecules and has a typical red frequency and red wavelength. You cannot
> change the characteristic frequency of a light wave by passing it through a
> typical transparent material.
>
> The perceived slow down is simply that the red light has to make so many
> stops along the way. It gets absorbed and re-emitted millions of times. I
> tell my kids it is like traveling on I-95 for a family trip at 70MPH for an
> entire trip, but making several pit stops for potty and drinks. The AVERAGE
> speed of the path decreases, not the instantaneous speed of the traveler at
> any given driving time. So, the last red photon spit out by an electron has
> the same properties as the original photon that entered the other side of
> the glass. Or water. The slowdown and wavelength shift are simply the
> culmination of traveling at 'c' and making a Bajillion pitstops along the
> way.
>
> I can't remember which text author, maybe Hewitt, had a nice description
> and diagram of this years ago when texts were still made from paper...
>
> Hope this helps. Better yet, hope this is sorta right...
>
> -DT