Question

Answer the following questions:
(a) What is total internal reflection?
(b) State two conditions necessary for the total internal reflection to occur.
(c) Draw diagrams to illustrate the total internal reflection.[5 marks]

Answer 1

(a) Total internal reflection is the phenomenon which occurs when light travels from denser to rarer medium at a large angle of incidence. [0.5 Marks]
In total internal reflection, light is reflected back to the incident medium and almost no light enters the second medium. The reflected ray follows the laws of reflection. [0.5 Marks]

(b) For total internal reflection to occur, two conditions must be met:

• The angle of incidence of the light ray must exceed the critical angle of the interface. [1 Mark]
• Ray must travel from denser to rarer medium. [1 Mark]

(c) In the figure shown below, the third case corresponds to that of total internal reflection.
[2 Marks]