$A$ 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 $20 \%$. The angle of deviation is

Pick out the wrong statement from the following:

As shown in the figure,a plane mirror is fixed at a height of $50\,cm$ from the bottom of a tank containing water $\left(\mu = \frac{4}{3}\right)$. The height of water in the tank is $8\,cm$. $A$ small bulb is placed at the bottom of the water tank. The distance of the image of the bulb formed by the mirror from the bottom of the tank is $......\,cm$.

$A$ glass slab of thickness $4 \,cm$ contains the same number of waves as in $x \,cm$ of water column when both are traversed by the same monochromatic light. If the refractive indices of glass and water for that light are $\frac{5}{3}$ and $\frac{4}{3}$ respectively,the value of $x$ will be

$AB$ is an object of length $l$ dipped in water at a depth of $d$. It is viewed from air at near-normal incidence. The length of the image is

One side of a glass slab is silvered as shown. $A$ ray of light is incident on the other side at an angle of incidence $i = 45^o$. The refractive index of the glass is $1.5$. The deviation of the ray of light from its initial path when it comes out of the slab is......$^o$.