For total internal reflection to take place, the angle of incidence i and the refractive index (μ) of the medium must satisfy the inequality
1sin i<μ
For total internal refection to take place
i>θC
or, sin i>sin θC
We know that, sin θC=1Refractive index of the medium=1μ
So, sin i>1μ
or, 1sin i<μ