CDS [2008 -II]

The phenomenon of mirage occurs due to which one of the following? 

(a) Polarisation of light

(b) Dispersion of light

(c) Diffraction of light

(d) Total internal reflection of light

Answer : D

Explanation: Total Internal Reflection (TIR): 

When a ray of light goes from denser to the rarer medium it bends away from the normal and as the angle of incidence in denser medium increases, the angle of refraction in the rarer medium also increases and at a certain angle, the angle of refraction becomes 90°, this angle of incidence is called critical angle (C).

When the Angle of incidence exceeds the critical angle then light ray comes back into the same medium after reflection from the interface. This phenomenon is called Total internal reflection (TIR).

• Reflection is the phenomenon of bouncing back of light after striking any surface.
• Refraction occurs when a ray of light bends while moving from one medium to another.
• Diffraction is the phenomenon that occurs when a ray of light bends at a sharp edge.