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]
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Solution
(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]