Physics

Problem

In figure, the optical fiber is

l = 2

m long and has a diameter of

d = 20 \mu\text{m}

. If a ray of light is incident on one end of the fiber at angle

\theta_1 = 40^\circ

, the number of reflections it makes before emerging from the other end is close to : (refractive index of fiber is 1.31 and

\sin 40^\circ = 0.64

) [NCERT : PL-231 | 8 April 2019 I] ![Diagram showing a ray of light entering an optical fiber at an angle of 40 degrees relative to the normal (dashed line). The ray undergoes total internal reflection inside the fiber, traveling zig-zag. The diameter of the fiber is labeled d.](https://storage.googleapis.com/diraq-contents/homework-question-parsing/marker/20260106T182719Z/1983f081940a4107b423d212683ff37a/30a26f2d17ca95672702bf50fb4f0242_img.jpg) (a) 55000 (b) 66000 (c) 45000 (d) 57000

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