For an interface with the free charge density of =0 from(Dnl -Dm2) - Of we have Di cos 01- D2 cos 82=0 or r1e0E1 cos 61= Er2E0 E2 cos 02 From the tangential component Et1= Et2, we have E1 sin 01- E2 sin B2 Combining these two equations yields tan T tan e2 Er2 The medium with the larger relative permittivity cr has a larger angle 0 from the normal