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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

3.3 `mu`s

B

6.6 `mu`s

C

5.7 `mu`s

D

3.85 `mu`s

Text Solution

Verified by Experts

The correct Answer is:
D
(d) When total internal reflection just takes place from lateral surface, i=C i.e., `60^(@)=C`
`rArr sin 60^(@)=sinC= 1/murArrmu=2/sqrt3`
Time taken by light to traverse some distance in a medium,
`t=(mux)/c=(2/sqrt3xx10^(3))/(3xx10^(8))=3.85mus`
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DC PANDEY ENGLISH-RAY OPTICS-Exercise
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