The refractive index of a given transparent medium is 1.4. Which of the following is the minimum internal angle for total internal reflection to take place in the medium?
- 30o
- 36o
- 44o
-
46o
- 54o
The correct answer is: D
Explanation
Critical angle Sin \(\theta\)\(_c\) = \(\frac{n_2}{n_1}\)
where n\(_1\) = refractive index of the medium ( 1.4 given )
n\(_2\) = refractive index of the second medium( air ≈ 1.0)
Sin\(\theta\)\(_c\) = \(\frac{1}{1.4}\) ≈ 0.7143
\(\theta\)\ = Sin\(^{-1}\)( 0.7143) ≈ 45.58º ≈ 46º
The minimum internal angle for total internal reflection to take place in the medium is approximately = 46º