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Which of the following is not due to total internal reflection?
A
Brilliance of diamond
B
Working of optical fibre
C
Difference between apparent and real depth of a pond
D
Mirage on hot summer days
Detailed Solution
Brilliance of diamond: its critical angle is very small (about $24.4^\circ$), so light entering it suffers repeated total internal reflections.
Optical fibre: light is guided along the fibre by repeated total internal reflection at the core–cladding boundary.
Mirage: light from an object is totally internally reflected at the hot, rarer air layers near the ground.
Apparent depth of a pond: light from the bottom simply bends away from the normal on passing from water to air, making the pond look shallower. This is ordinary refraction; no total internal reflection is involved.
Hence the difference between apparent and real depth of a pond is not due to total internal reflection.
Optical fibre: light is guided along the fibre by repeated total internal reflection at the core–cladding boundary.
Mirage: light from an object is totally internally reflected at the hot, rarer air layers near the ground.
Apparent depth of a pond: light from the bottom simply bends away from the normal on passing from water to air, making the pond look shallower. This is ordinary refraction; no total internal reflection is involved.
Hence the difference between apparent and real depth of a pond is not due to total internal reflection.