Question
Physics Question on Ray optics and optical instruments
If the critical angle for total internal reflection from medium to vacuum is 30∘ , the velocity of light in medium is
A
3×108m/s
B
1.5×108m/s
C
6×108m/s
D
3×108m/s
Answer
1.5×108m/s
Explanation
Solution
Refractive index medium μ=sinC1 where C is critical angle. Given, C=30∘ ∴μ=sin30∘1=1/21=2 From Snell's law μ=vmv0 where v0 is speed of light in vacuum and vm the velocity in medium. ∴vm=23×108 =1.5×108m/s