Question

7. A ray of light has a frequency of f = 6 x 1014 Hz. It enters into a flat surface of glass from air with an angle of incidence of 0 = 30° to the surface normal. The refractive index of the glass at this frequency is 1.4. Note that the refractive index of air is 1.0, and the speed of light in air is c= 3 x 108 m/s. (a) (1 mark) What is the wavelength of the light in the glass? (b) (3 marks) What is the angle of refraction as the light enters the glass? (c) (3 marks) What is the critical angle of incidence (where internal reflection just occurs) at this frequency inside the glass?

Answer 1

- Given f = 6X10" HZ G= 3x108 mis air M=1 o is the angle of incidence. Surface Glass x My Main =1, H = 1.4 ② wavelength, a= § - 3x10 mis = 5x10 T m = 5oonm 2 61014 S- - o using snell's law Main sine a Molave sin b d is the angle of refraction. 1.3in 30 = 1.4 Sin i n Sind= 0.5 (singo' = 0.5) 1.4 0 = sin(0,5) = 20.95 — 21 O when critical angle is defined on incidence that provides an angle of ao .. o = Ocnit 6 = 90 the of angle of Refraction In this case, the light is incident from water glass. Now Snell's law 1 g sino = Masino it - Ti singo ! glais pour Ocnit = sini tiny) = 45.6 Mno).