Notes

Total Internal Reflection…

Total Internal Reflection – In this situation, when the angle of incidence exceeds a particular angle, the incident ray comes back into first medium (denser medium). This angle is called critical angle (θ_C). This whole phenomenon is called total internal reflection. At critical angle, there is no refracted ray found because ∠r = 90°.
sinθ_C/sin90° = μ_rarer/μ_denser = μ_r/μ_d
⇒ sinθ_C = μ_r/μ_d ⇒ [θ_C = sin^-1 (μ_r/μ_d)]
where, μ_r = Refractive index of rarer medium
and μ_d = Refractive index of denser medium