# Simple? optics

1. Nov 30, 2004

### rayjohn01

I have a light ray travelling through air at 'c' , it then enters some ordinary glass say mu=1.5 , it slows down by mu. --- no problem.
According to the normal equation v = f . lambda , (velocity , frequency , wavelength) ,
'v' has slowed down from 'c' to 'c' / mu therefore the RHS must change

But what changes ?? 1.5 is a LOT.
if glass is a linear medium there seems no reason for 'f' to change , so it would appear that Lambda must .
when the ray exits the glass it changes back so what we see is what went in.
But what about the eye where the ray strikes the retina do we see an altered lambda different from the air ???????
Ray

Last edited: Nov 30, 2004
2. Dec 7, 2004

### SGT

You are correct. What changes is the wavelength. The wavelengths of the light that reaches your retina are those corresponding to the humor vitreous, that fills your eyeballs.

3. Dec 7, 2004

### Gonzolo

Yes we do. Another fun fact of physics (that, after all has been said, doesn't change much in our daily lives).

4. Dec 7, 2004

### rayjohn01

yes -- but

You are right Gonz , it is hardly earth shattering , and probably very old science -- so answer this -- if a ruby Laser enters a diamond then what is the color ( physical sense) of it inside the diamond -- did you think it was ruby ???? or what did you think ?
The color of the diamond (as seen ) is due to what ?
If I sandwich a film between glass does it change it's sensitivity to color ?
if so why and if not why.
Does the eye see -- frequency or wavelength - if the first then the ray entering the eye -- if the second the ray in the eye ?
The eye resolution is NOT due to the entering ray -- but the inside ray
which is 34% smaller .
Such questions are not earth shattereing but actually effect how we design things .
Actually you cannot say so quickly that it is the Vitreous Humor unless the rods and cones are actually embedded in this and indeed any media prior to the destruction of the light wave at atomic absorbsion .

Ray

Last edited: Dec 7, 2004
5. Dec 7, 2004

### Gonzolo

Our retina cells (and whatever chemical absorption that goes on in there) are affected by photon energy E = hf = hv/lambda, so strictly speaking "colour" is determined by frequency, more than wavelength. So suppose we immersed a "waterproof photodiode detector" in water or alcool, which has n > 1, I believe it would behave as would in air with the Ruby frequency.

As far as I know, it doesn't (unless it heats up, or allows internal reflection and some nonlinear effect happens, depending on what film you use).

Not earth shattering for normally-sighted people, but I agree it can matter for design, maybe even for some optometrist researchers.

Last edited by a moderator: Dec 7, 2004
6. Dec 7, 2004

### rayjohn01

I think on the film you are mostly correct , but not for stated reasons , the active grains are already embedded within a media of it's own refractive index and therefore do not careabout the glass except that is for grains which are within a wavelength of the light within either media -- they maybe schitzophrenic .
Ray.

7. Dec 8, 2004

### Gonzolo

That makes a lot of sense. My "stated reasons" (in parenthesis) were simply rough examples of how sandwiching between glass might affect properties of some films. I still think grain activity (absorption) is determined by frequency.