Refraction Aim: To determine the refractive index of glass and the critical angle and to observe the path of light rays passing through a glass block. Theory: i. What is the refractive index of a medium? What symbol is it denoted by? ii. Does it have a unit? Why or why not? iii. Define a. The normal b. Angle of incidence c. The angle of refraction Variables: Manipulated (Independent) Controlled Responding (Dependent) Apparatus: Optical pins/ray box Glass block with lower surface painted white. Protractor Ruler Pencil White paper (Legal size) Diagram of Apparatus: Figure 1 Procedure: 1. Place the glass block with the white painted surface on the paper and its long side along line AOB in the figure above. Draw the outline of the block onto your paper. 2. Mark the normal to the block at O. 3. Align the lamp and the single slit so that a beam of light is incident on the block at O at an angle of incidence of 10 4. Draw in the incident ray, the refracted ray and the emergent ray; measure the exact angle of each to the surface normal with a protractor and record