When the angle of incidence in the denser medium equals the critical angle, what is the angle of refraction in the rarer medium?

1. As light goes from denser to rarer medium it bends away from the normal, so r is larger than i. 2. Increasing i increases r; for a particular value of i, r becomes exactly 90 degrees. 3. The chapter defines this value of i as the critical angle, at which r = 90 degrees. 4. For incidence beyond the critical angle, total internal reflection occurs instead of refraction. _Source: Balbharati (Maharashtra Board) Class 10 Science & Technology, Ch 6 "Refraction of Light", p.87_