- The Dipole Are A 5 The Dispersion Relation For Electromagnetic Waves With Angular Frequency W And Wavevec Tor K In A M 1 (75.02 KiB) Viewed 50 times
the dipole. are A.5 The dispersion relation for electromagnetic waves with angular frequency w and wavevec- tor k in a medium with refractive index n is w = ck/n(w). Show that the group velocity of these waves, Vg, is given by [3] с Ug = n+w dn/dw K For sufficiently high w, the refractive index has the form n 1-a/w² where a is a positive constant. Show that v, < c extremely high w. [2] [5] A.6 Estimate the value of the refractive index for the perfect quarter wave anti-reflection coating for glass (ng = 1.5), stating any approximations you make. of it Continued overleaf... PAGE 2 PRINTED: TUESDAY 18TH APRIL, 2017