Why Do Longer Wavelengths Go Slower in Glass?

[exmarine]

TL;DR

Thinking about what the Weber telescope might see different than the Hubble. Does the light also get separated into different wavelengths like in a prism?

I reviewed the derivation / solution of that GRT problem and do not see any dependence on the wavelength of the light. Is that correct, or am I missing something?

This makes me wonder about my understanding of how prisms work. How or why do longer wavelengths go slower in glass than shorter wavelength?

Just curious. Thanks.

 

[vanhees71]

I don't know, why you think this has something to do with GR, but here's the "classical" explanation for the index of refraction by Feynman:

https://www.feynmanlectures.caltech.edu/I_31.html

 

[exmarine]

Webb telescope.
I don't think prisms have anything to do with GRT.
Thanks for the link.

 

[russ_watters]

Yes, Webb does have that capability. It's a pretty key/core function of research telescopes:
https://webbtelescope.org/resource-...lterUUID=a776e097-0c60-421c-baec-1d8ad049bfb0

 

[dlgoff]

here's the "classical" explanation for the index of refraction by Feynman:

Feynman's explanations about light are all very good. I have DVDs of all his lectures.

 

[PeterDonis]

I reviewed the derivation / solution of that GRT problem and do not see any dependence on the wavelength of the light. Is that correct, or am I missing something?

It's correct; light bending by gravity is wavelength independent. That's because it's a property of the geometry of spacetime, which is the same for all wavelengths of light.

This makes me wonder about my understanding of how prisms work. How or why do longer wavelengths go slower in glass than shorter wavelength?

The effects of prisms are not due to the geometry of spacetime but to the material properties of the prism and its shape. So there is no valid analogy between how prisms work (and refraction of light by material media in general) and light bending by gravity.

 

[dlgoff]

Feynman's explanations about light are all very good. I have DVDs of all his lectures.

I've got 7 DVDs; The Character of Physical Law:

 

[dlgoff]

I've also have Richard Feynman's Quantum Mechanics lectures:
1) Photons Corpuscles of Light
2) Reflection
3) Electron Interactions
4) Problems in QED and The Standard Model of Particle Physics

edit: I hope I'm not too much off topic here. If so, sorry about that.

 

[exmarine]

I also have all his books I could find.

 

[dlgoff]

I decided to check my backup drive to see if I had anything from Richard Feynman and low and behold I found lecture videos on these subjects in a folder (The Character of Physical Law):

Lecture 1 Law of Gravitation
Lecture 2 Relation of Mathematics and Physics
Lecture 3 Great Conservation Principles
Lecture 4 Symmetry in Physical Law
Lecture 5 Distinction of Past and Future
Lecture 6 Probability & Uncertainty-the quantum mechanical view of nature
Lecture 7 Seeking New Laws

edit: I guess these are the same ones I showed in post 7 above.