$A$ fish and a bird are moving as shown in the figure. Find the velocity of the bird as observed by the fish.

What is lateral shift?

$A$ ray of light travelling through a rarer medium is incident at a very small angle '$i$' on a glass slab,and after refraction,its velocity is reduced by $25 \%$. The angle of deviation is:

$A$ 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

Two immiscible liquids of refractive indices $\frac{8}{5}$ and $\frac{3}{2}$ respectively are put in a beaker as shown in the figure. The height of each column is $6 \,cm$. $A$ coin is placed at the bottom of the beaker. For near normal vision,the apparent depth of the coin is $\frac{\alpha}{4} \,cm$. The value of $\alpha$ is . . . . . . .

$A$ fish at a depth of $12 \, cm$ in water is viewed by an observer on the bank of a lake. To what height the image of the fish is raised? $....... \, cm$ (Refractive index of lake water $= 4/3$)