2. What does a fish in a lake see when it looks up toward the smooth surface of a lake? 3. Start with snell's Law and and the information in Figure 2, and derive (2).\fincoming light F air , n = 1 glass , n 0 dark illuminated Figure 2. Light incident at point 0 scatters and produces a dark circle and an illuminated ring. Using Snell's Law and trigonometry, the index of refraction of the glass plate can be found as VD2 + 1612 n = D (2)incoming light Figure 3. Light incident at point 0 is scattered and produces internal reflections at the glassliquid and liquidair boundaries. Using Snell's Law. trigonometry, and the information from Figure 3. the index of refraction of the liquid. 11'. can be found if n, t, and D are known. The expression is HD n' = (3) JD2 +1613