$A$ thin oil layer floats on water. $A$ ray of light making an angle of incidence of $40^o$ shines on the oil layer. The angle of refraction of the light ray in water is......$^o$ $({\mu _{oil}} = 1.45, {\mu _{water}} = 1.33)$

$A$ monochromatic beam of light is travelling from medium $A$ of refractive index $n_{1}$ to a medium $B$ of refractive index $n_{2}$. In the medium $A$,there are $x$ number of waves in a certain distance. In the medium $B$,there are $y$ number of waves in the same distance. Then,the refractive index of medium $A$ with respect to medium $B$ is

$A$ light ray undergoes refraction from air to water,water to glass,and finally from glass back to air. If the emergent ray is parallel to the incident ray,which of the following relations is correct? ($n_{a}, n_{w}, n_{g}$ represent the refractive indices of air,water,and glass respectively.)

An observer can see through a pinhole,the top end of a thin rod of height $h$,placed as shown in the figure. The beaker's height is $3h$ and its radius is $h$. When the beaker is filled with a liquid up to a height $2h$,he can see the lower end of the rod. Then the refractive index of the liquid is

The refractive index of glass is $3/2$ and the refractive index of water is $4/3$. If the speed of light in glass is $2.00 \times 10^8 \ m/s$,the speed of light in water will be:

When can it be assumed that light moves in a straight line?