Materials called NIMs with an unusual value for this quantity were first realized using split-ring resonators. (10[3]-5[1])An empirical formula for this quantity (10[1])is expanded in negative even powers of wavelength and (10[1])becomes (10[1])inaccurate (10[1])in regions of anomalous dispersion. (10[2])The (10[1])imaginary part (10[1])of complex (10[2])values (10[1])for this quantity (10[6])models (10[2])attenuation. (10[8]-5[3])Since most materials (10[1])have negligible magnetic susceptibility, this value is approximately given by the square root of relative permittivity. (10[2]-5[1])A decrease (-5[1])of this quantity (10[1])across an (10[1])interface (10[1])enables (10[2])rays (10[1])to undergo (10[1])total (10[1])internal (10[1])reflection. (10[7]-5[4])The ratio (10[3])of the sines (10[3])of (10[1])the (-5[1])angles (10[4]-5[1])of (10[1])incidence (10[6])and (10[1]-5[1])refraction equals (-5[1])the ratio of two values of this (10[1])quantity (10[3]-5[1])according (10[1])to (-5[1])Snell’s (-5[1])law. (10[2]-5[3])For (-5[1])10 points, (10[1])name this quantity (10[1])that is the ratio of speed of light in vacuum (10[2])to (10[1])its speed (10[1])in a material. (10[2])■END■ (10[14]0[4])