The Fizeau experiment showed that in luminiferous aether theory, the Fresnel drag coefficient for propagation of light in a medium is equal to one minus one over this quantity squared.
For an oscillating electric field, the square of this quantity can be expressed as the electrical permittivity plus the quantity four-pi-i times the electrical conductivity divided by the angular frequency. The Fizeau experiment showed that in luminiferous aether theory, the Fresnel drag coefficient for propagation of light in a medium is equal to one minus one over this quantity squared. This quantity experiences a shift that is linear or quadratic in the applied electric field in the Pockels and Kerr effects, resulting in birefringence. Fermat's principle of least time can be used to derive a relation in which a ratio of values of this quantity equals a ratio of sines of angles; that law is Snell's law. For 10 points, name this ratio of the speed of light in a vacuum to the speed of light in a medium.
For an oscillating electric field, the square of this quantity can be expressed as the electrical permittivity plus the quantity four-pi-i times the electrical conductivity divided by the angular frequency.
index of refraction [or refractive index]