In figure, the optical fiber is l=2 m long and has a diameter of d =20 μ m. If a ray of light is incident on one end of the fiber at angle θ_1=40^°,…

In figure, the optical fiber is $\displaystyle l=2 \mathrm{~m}$ long and has a diameter of $\displaystyle \mathrm{d}=20 \mu \mathrm{~m}$. If a ray of light is incident on one end of the fiber at angle $\displaystyle \theta_1=40^{\circ}$, the number of reflections it makes before emerging from the other end is close to : (refractive index of fiber is $\displaystyle 1.31$ and $\displaystyle \sin 40^{\circ}=0.64$ )