Question

# If the critical angle for total internal reflection from a medium to vacuum is 30o. Then velocity of light in the medium is:

A
3×108 m/s
B
4.5×108 m/s
C
1.5×108 m/s
D
2.5×108 m/s
Solution
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#### Critical angle for total internal reflection θc=30oAs we know, refractive index of air medium nair=1Refractive index of the medium n=1sinθc∴ n=1sin30o=10.5⟹ n=2Velocity of light in medium v=cn∴ v=3×1082=1.5×108m/s

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