Question

1. (20pts) A figure shows a light ray entering an optical fiber from air and being transmitted through the fiber by total internal reflection. A. (10 pts) If the index of refraction of the fiber is nu 1.3 what is the maximum value of the angle the entering ray makes with the normal to the flat end of the fiber, for which total internal reflection occurs? B. (10 pts) When n is greater than a certain value, no, the light ray can enter at any angle, 0 < < 90° and total internal reflection occurs inside the fiber. What is no? air optical fiber

Answer 1

Soth n=113 H 90-0, let ac be critical angle for which total internal reflection occurs at A. in Sinde = 1x Singola Oc= Sini (1) .: , >, Qc = Sin-1() 50:29' 0 > 50.29 .: -90-0, ad 39.71 Now using Shell's law 1x Since=1+34 Sind Sino ( 1.3 * Sin (39.77) OL 56.11'. Omod= 56.170 for which total internal 56:17] Pyllehon occure. 100 < 90' 1x sino = nx sina nsinal Sind at 9 d < Sin' () in 0,= 9ood 0,7 Go - Sin() nsinca, = 1x Singo' nx Sin (90-sin' (!)771 na 1 1 - 1 / 2 ) > 1 nx coorsin-l(+] = n2-171 - nx V 1-1/12 " = n2>2 2) ny2 no = √2 l