A ray of light passes through a prism shaped like an equilateral triangle. The ray is incident horizontally on the prism as shown. The prism is made of glass with index of refraction ng = 1.5 and is surrounded by air. When 1 is changed to a certain value, total internal reflection (TIR) occurs. Which of the following statements are true? (note: diagram may not be drawn to scale) (a) As shown in the diagram, 2 is 19.5 degrees (b) As shown in the diagram, 2 is 35.3 degrees (c) As shown in the diagram, 2 is 70.5 degrees (d) 1 must be increased for TIR to occur. (e) 1 must be decreased for TIR to occur. (f) TIR will occur at the first interface (between 1 and 2). (g) TIR will occur at the 2nd face (between 3 and 4)