Rohit is travelling by a car through a highway on a hot summer afternoon. The road in front of him appears momentarily wet as shown in the picture below.
(a) Name and define the phenomenon responsible for this.
(b) Provide another example that demonstrates the same phenomenon.
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(a) The phenomenon is Total internal reflection.
Total internal reflection is the phenomenon in which a ray of light travelling from an optically denser medium to an optically rarer medium is completely reflected back into the denser medium when the angle of incidence is greater than the critical angle.
On a hot afternoon the air near the road is hot and rarer, while the air above it is cooler and denser. Light coming from the sky travels from the denser upper layers to the rarer lower layers, bending away from the normal at each layer, until it strikes a layer at an angle greater than the critical angle. It is then totally internally reflected and reaches the driver's eye from below, so the driver sees the image of the sky on the road and the road appears wet.
(b) A diamond sparkles because of total internal reflection.