Humidity changes the speed of light in air?

Factual Questions
1

Is there a measurable difference of the speed of light in dry air vs humid air?

If so, do you know how you can calulate the difference based on an absolute or relative humidity measurement?

2

The speed of light in a medium is 1/sqrt(u*e). u = magnetic permeability of the medium, e = electrical permittivity of the medium. There is a measureable difference in air v. vacuum. I know that the speed varies with temperature and pressure but I’m not sure about humidity. The transmission of light through a medium is quite complex because the medium treats different wavelengths differently. This results in scattering, making the sky blue for example, and dispersion, as when light is refracted by rain drops to make a rainbos.

Someone else will have to direct you to tables for the speed of light in various atmospheric conditions. Try Google, or Yahoo! search

3

Site.

Here’s a calculator linked on that site to calculate light wavelengths based on temp, pressure, and humidty.

And since I’m bored, here are some more links.

Seriously, Google is your friend.