1. The problem statement, all variables and given/known data Glass has a permeability of ε=2.0 and relative permeability μ=1. Electromagnetic radiation of angular frequency ω=2.8x109 s-1. travels through the glass. Calculate a) refractive index b) speed of radiation c) frequency of radiation d) wavenumber of radiation a, b and c are straightforward but d I have questions for 2. Relevant equations n=√ε n=c/v f=ω/2∏ v=ω/k ω=2∏f k=n2∏f/v 3. The attempt at a solution a) refractive index, n=√ε = √2 b) speed of radiation travelling through glass, n = c/v so v = c/n v = 3.0x108 ms-1 / √2 v = 2.12x108 ms-1 c) frequency of radiation, f = ω/2∏ f = 2.8x109 s-1 / 2∏ f = 4.46x106 Hz d)wavenumber of radiation now v = ω/k - where k is the wavenumber so make k the subject k = ω/v k = 2.8x109 s-1 / 2.12x108 ms-1 k = 13.2 BUT ω = 2∏f and k=n2∏f/v so k = (2x2∏x 4.46x106) / 2.12x108 ms-1 k = 0.132 So which is right, please?