Materials called NIMs with an unusual value for this quantity were first realized using split-ring resonators. An empirical formula for this quantity is expanded in negative even powers of wavelength and becomes inaccurate in regions of anomalous dispersion. The (10[1])imaginary part of complex values for this quantity models attenuation. (-5[1])Since most materials have negligible magnetic susceptibility, this value is approximately given by the square root of relative permittivity. A decrease of this quantity across an interface enables rays to undergo total internal reflection. The ratio of the sines (10[2])of the angles of incidence and (-5[1])refraction equals the ratio of two values of this quantity according to Snell’s law. (-5[1])For 10 points, name this quantity that is the ratio of speed of light in vacuum to its speed in a material. ■END■ (10[2])