There is a tiny LED bulb, at the centre of the bottom of a cylindrical vessel of diameter 6 cm. Height of the vessel is 4 cm
The beaker is filled completely with an optically dense liquid. The bulb is visible from any inclined position but just visible, if seen along the edge of the beaker. Determine the reflective index of the liquid.

Water drips from a tap at the rate of 4 drops in every 3 seconds. Volume of one drop of 0.4 cm^3 , If dripped water is collected in a cylinder vessel of height 7 cm and diameter is 8 cm. In what times vessel be completely filled? What is the bolume of water collected? How many such vessels will be completely filled in 3 hours in 40 minutes?