(a) Write the necessary conditions for the phenomenon of total internal reflection to occur. (b) Write the relation between the refractive index and critical angle for a given pair of optical media.

(a) Necessary conditions for total internal reflection to occur are:
(i) The incident ray on the interface should travel in optically denser medium
(iii) The angle of incidence should be greater than the critical angle for the given pair of optical media
(b) μ = 1/sinC or μ₀ = 1/sinC
Where a and b are the rarer and denser media respectively. C is the critical angle for the given pair of optical media