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A light ray from air is incident (as sho...

A light ray from air is incident (as shown in figure ) at one end of a glass fiber ( refractive index `mu=1.5)` making an incidence angle of `60^(@)` on the lateral surface, so that it undergoes a total internal reflection. How much time would it take to traverse the straight fiber of length `1 km `?

A

3.33 `mu` s

B

6.67`mu`s

C

5.77 `mu`s

D

3.85 `mu`s

Text Solution

Verified by Experts

The correct Answer is:
D
`sin i_(c ) = (1)/(n) rArr n = (1)/(sin i_(c )) = (2)/(sqrt(3))`
Time (t) = `("Distance")/("Velocity") = (nx)/(c )`
`= ((2)/(sqrt(3)) xx 10^(3) )/(3 xx 10^(8)) = 3.85 xx 10^(-6) " sec " rArr t = 3.85 mu `s.
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