Subject: re3: Do other fields also bend where materials of different densities meet?

reply question to answer 
http://www.madsci.org/posts/1148865566.Ph.r.html
So, light bends when it enters materials with different indecies at an angle.
This permit the construction of lenses to redirect light in order to focus,
concentrate, diverge, or make parallal the beam. 
Fields, such as electric (and aparently magnetic due to their relationship) also
bend when moving between materials at an angle. However, unlike light, the
charecteristic of the materials that cause this is permittivity. Couldn't this
also permit the construction of electric/magnetic field lenses that could focus,
concentrate, diverge, or make parallal the field. Why not go a step further and
try to do the same with gravity. Except, I don't know the charecteristic of a
medium akin to permittivity and to index of refraction for gravity. Any truth to
this idea?

-Roman R.

Re: re3: Do other fields also bend where materials of different densities meet?