Why do electromagnetic waves travel slower in other mediums?

[DarylMBCP]

Hi guys, I'm not rlly sure why certain electromagnetic waves (in the electromagnetic spectrum) travel slower in other mediums apart from in a vacuum (all the waves travel at the same speed)? I tried to search this and found out tht the wavelength of waves decreases when in a denser medium like water but does this mean tht the wavelength decreases by a different amount for each wave, if not, the speed of all the electromagnetic waves will be the same due to speed = wavelength x frequency?

 

[Dadface]

Hello Daryl,the refractive index of a medium =speed in vacuum/speed in medium=wavelength in vacuum/wavelength in medium.Generally speaking different frequencies have different refractive indices so I think that in general the answer to your question is yes.This seems to be true for the visible part of the spectrum,hence the phenomenom of dispersion, but whether there are other parts of the spectrum or other media where dispersion does not happen I do not know.

 

[DarylMBCP]

Ok, I get it. Thnks for the help.