Is all electromagnetic radiation refracted when passing through a denser medium?

[Humberto]

Or is it only visible light?

 

[supersunbird]

All

 

[agentrfr]

*Most*

But that really depends on the angle of the incidence ray, not really the frequency of EMR. In general though, assuming you aren't greater than the critical angle, it will be refracted.

For more equations and explanations see wiki http://en.wikipedia.org/wiki/Refraction
http://hyperphysics.phy-astr.gsu.edu/hbase/geoopt/refr.html