(b)State two conditions necessary for total internal reflection to occur.

(c)Draw diagrams to illustrate critical angle and total internal reflection.

Solution:

(a) Total internal reflection: A beam of light travelling through a denser medium is totally reflected back into the denser medium when it strikes the surface of a rarer medium at an angle of incidence greater than the critical angle for the pair of media. Total internal reflection is the term for this phenomena.

(b) There are two prerequisites for total internal reflection:

(i) The light must pass through a denser media before reaching a rarer medium.

(ii) The angle of incidence for the pair of media must be greater than the critical angle.

(c) When the incidence angle is greater than the critical angle, the total internal reflection is shown in the diagram below.