A mark is made at the bottom of a beaker and a microscope is focussed on it.the microscope is then raised through 0.015 m.To what height water must be poured into the beaker to bring the mark again into focus?Given`a^mu_w = 4//3`.

A microscope is focussed ona mark on a piece of paper then a slab of glass of thickness 3 cm and refractive index 1.5 is placed over the mark.How should the microscope be moved to get the mark in focus again?

A tank is filled with water to a height of 12.5 cm. The apparent depth of a needle lying at the bottom of the tank is measured by a microscope to be 9.4 cm. What is the refractive index of water? If water is replaced by a liquid of refractive index 1.63 up to the same height, by what distance would the microscope have to be moved to focus on the needle again?

Water is dripping out from a conical funnel at a uniform rate of 4c m^3//sec through a tiny hole at the vertex in the bottom. When the slant height of the water is 3cm , find the rate of decrease of the slant height of the water-cone. Given that the vertical angle of the funnel is 120^0dot