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Asked in CBSE AIPMT 2011 · Total internal reflection and optical fibres
Idea: total internal reflection needs light travelling from a denser medium towards a rarer one at more than the critical angle, and it returns the light entirely.
A pond looks shallower than it is because rays leaving the water are bent away from the normal as they cross the surface.
Those rays do cross the surface, so nothing is turned back and no total internal reflection takes place; it is ordinary refraction.
The mirage, the brilliance of diamond and the optical fibre all depend on light being turned back completely at a boundary.
So the odd one out is the difference between apparent and real depth of a pond.
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