1. A set of 4 identical mirrors are arranged such that they form a pentagonal structure of 4 sides (imagine a pentagon with each side of unit length, as we have investigated before, and remove one side, this is analogous to a so-called 3-walled-box with an additional edge). If a light ray enters the open edge at a 45 degree angle directly in the center of the edge, what angle does it exit the same edge at after reflecting off the mirrors? 2. A light ray initially in water enters a transparent substance at an angle of incidence of 32, and the transmitted ray is refracted at an angle of 120. Calculate the speed of light in the transparent substance. 3. An unknown material (n = 1.78) is poured into a container made of crown glass (n = 1.52). What is the critical angle for total internal reflection of a light ray in the liquid when it is incident on the liquid-to-glass surface? 4. What should the angle of incidence be if the light ray enters the unknown material from air (n = 1.00)