A coin is placed at the bottom of a clear glass vessel. An observer moves herself to a position where the coin goes just out of sight of her eyes. Keeping her eyes in that position, she asks her friend to pour some water, gradually into the glass vessel.
(a) What would she observe?
(b) Name the phenomenon involved in this observation.
(c) Draw a neat labelled diagram to justify your answer.
(a) Once water is filled in the vessel, the coin becomes visible to the observer.
(b) Refraction of light.
c) A coin at the bottom of a (initially empty) cup, (that was not visible to the eye) becomes visible after some water is poured into the cup.