Questions and Exercises 1. Does total internal reflection occur if the refraction of light is passing from air into water? Why? 2. Use Snell's law (no sina = n, sin , ) to explain why 0, is greater than 0. in Fig. 2. 3. In Fig. 2, if we increase the index n, but keep n, no Figure 2 shows that total internal reflection will occur if the two conditions are satisfied: (a) no >n , ( b ) 0. zec Critical angle Total Internal Retad reflection --,r=90 Water Figure 2 Total internal reflection at water / air interface 4. Focal point and center of curvature of concave and convex mirrors (a) Concave mirror Parallel rays reflecting from a concave mirror pass through the focal point F, which is the hal way between the surface of the mirror and the center of curvature. (b) Convex mirror When parallel rays reflecting from a convex mirror, they diverge as if originating from a focal point F half way between the surface of the mirror and the center of curvature