4. A sheet of plastic has an index of refraction ngrass = 1.55 and is surrounded by air. Assume that the index of refraction for air is nan: 1.00. Light is incident on the sheet of glass at an angle of incidence of 58", as shown in the figure below. a. Calculate the speed of the light in the glass. b. Explain why the light slows down when entering the glass. c. Draw 2 sketches. One of the reflected ray that bounces back into the air, and one of the refracted ray it travels in the glass on the diagram below. Make sure to label each ray as either the reflection or refraction. 58 degrees Air n\" = 1.00