The refractive index of glass is $1.6$ and the speed of light in glass will be . . . . . . . Speed of light in vacuum is $3 \times 10^{8} \,m \,s^{-1}$.

$A$ vessel of height $2d$ is half-filled with a liquid of refractive index $\sqrt{2}$ and the other half with a liquid of refractive index $n$ (the given liquids are immiscible). Then the apparent depth of the inner surface of the bottom of the vessel (neglecting the thickness of the bottom of the vessel) will be

$A$ ray of light is incident at the glass-water interface at an angle $i$. It emerges finally parallel to the surface of water. If the refractive index of water is $\mu_w = 4/3$,then the value of the refractive index of glass $\mu_g$ is:

The refractive index of air is $1.0003$. The thickness of an air column that will contain one more wavelength of yellow light $(6000 \mathring A)$ than in the same thickness in a vacuum is:

An object is immersed in a fluid. In order that the object becomes invisible,it should

$A$ beaker containing liquid is placed on a table,underneath a microscope which can be moved along a vertical scale. The microscope is focused,through the liquid,onto a mark on the table when the reading on the scale is $a$. It is next focused on the upper surface of the liquid and the reading is $b$. More liquid is added and the observations are repeated; the corresponding readings are $c$ and $d$. The refractive index of the liquid is