A diamond glitters in light because of its high refraction index of 2,42 and the small critical angle of the diamond-air boundary.
1. Calculate the critical angle of a diamond-air interface.
Take the refraction index of air as 1. (4)
The angle of incidence of light at the diamond-air interface is increased to 30°.
2. Redraw the diagram below and complete the path of ray of light. (2)
3. Name the phenomenon that will now be observed at the diamond-air interface. (1)
4. What are the TWO CONDITIONS that are necessary for the phenomenon in QUESTION 9.3 to happen? (2)
5. Name the medical instrument used to examine internal parts of the body that makes use of the phenomenon in QUESTION 9.3. (1) 
Learners passed light from a ray box through a rectangular glass block to verify Snell’s law. The results obtained are used to draw the graph below.
1.Write down the independent variable. (1)
2.Write down the variable that must be controlled. (1)
3.Write down the conclusion that can be obtained from the graph. (2)
4.USE THE GRAPH to determine the refraction index of the glass block. (4)