## Speed of EM in a medium

Visible light propagates at less than c in water.

What about other wavelengths of EM? Do they all travel at the same reduced speed? I think not, but am not sure. If they travel at different speeds then Suzanna can be seen comin' round the mountain in certain wavelengths before others.

 PhysOrg.com physics news on PhysOrg.com >> Promising doped zirconia>> New X-ray method shows how frog embryos could help thwart disease>> Bringing life into focus
 Recognitions: Homework Help The speed of light in a medium varies a bit with the (vacuum) wavelength. That means changing refractive index (dispersion). http://refractiveindex.info/?gclid=C...FUFO3wodllwA_w ehild

 Quote by ImaLooser Visible light propagates at less than c in water. What about other wavelengths of EM? Do they all travel at the same reduced speed? I think not, but am not sure.
Not at the same reduced speed. This is how a prism splits light up. Different wavelengths are refracted differently.

 If they travel at different speeds then Suzanna can be seen comin' round the mountain in certain wavelengths before others.
If the mountain is a prism, you'll see multiple Suzannas split into all the colours of the rainbow.

## Speed of EM in a medium

 Quote by krd Not at the same reduced speed. This is how a prism splits light up. Different wavelengths are refracted differently. If the mountain is a prism, you'll see multiple Suzannas split into all the colours of the rainbow.
If the mountain is of glass and Suzanna suddenly materializes behind it, then you will see the a violet Suzanna first. If she then dematerializes, you see the red Suzanna last.

 The propagation velocity depends on the frequency and the material very significantly. Essentially, the delay in propagation in medium is caused by this process: the EM wave perturbs the atoms, they get "polarized", which creates internal EM field that interfers with the incoming EM, and the combined EM appears to travel slower. Obviously, this process depends on the material and the incoming radiation.