12. Physics 1999]
When a small lamp is held 1.5 m above the surface of
water in a tank, its image formed by reflection at the
surface appears to coincide with the image of the bot-
tom of the tank. (u of water = 4/3). The depth of the
tank is
(a) 2 m
(b) 1.5 m
(c) 1 m
(d) 4 m.