In figure, the optical fiber is \[l=2m\] long and has a diameter of \[d=20\mu m.\]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 \[\sin 40{}^\circ =0.64)\] |
A) 66000
B) 55000
C) 45000
D) 57000
Correct Answer: D
Solution :