Question
Physics Question on Ray optics and optical instruments
If the critical angle for total internal reflection from a medium to vacuum is 30∘ , then the speed of light in the medium is
A
6×108m/s
B
3×108m/s
C
2×108m/s
D
1.5×108m/s
Answer
1.5×108m/s
Explanation
Solution
Critical angle C=30∘ Refractive indexroman μ=sinC1=sin30∘1=2 ∴ Also μ=vc ∴ speed of light in medium v=μc=23×108 =1.5×108m/s