If the speed of light in vacuum is $C \ m/s$,then what is the velocity of light in a medium of refractive index $1.5$?

$A$ ray of light is incident at the glass-water interface at an angle $i$. It emerges finally parallel to the surface of water. The value of ${\mu _g}$ is (given refractive index of water ${\mu _w} = 4/3$):

There are certain materials developed in laboratories which have a negative refractive index. $A$ ray incident from air (medium $1$) into such a medium (medium $2$) shall follow a path given by

Green light of wavelength $5460 \mathring{A}$ is incident on an air-glass interface. If the refractive index of glass is $1.5$,the wavelength of light in glass would be ........ $\mathring{A}$.

In a medium,the speed of a light wave decreases to $0.2$ times its speed in free space. The ratio of relative permittivity to the refractive index of the medium is $x: 1$. The value of $x$ is $...........$ (Given: speed of light in free space $= 3 \times 10^8 \ m \ s^{-1}$ and for the given medium $\mu_r = 1$)

In finding out the refractive index of a glass slab,the following observations were made through a travelling microscope: $50$ vernier scale divisions $= 49$ $MSD$; $20$ divisions on the main scale in each $cm$. For a mark on paper:
$MSR = 8.45 \ cm, VC = 26$
For the mark on paper seen through the slab:
$MSR = 7.12 \ cm, VC = 41$
For a powder particle on the top surface of the glass slab:
$MSR = 4.05 \ cm, VC = 1$
($MSR =$ Main Scale Reading,$VC =$ Vernier Coincidence)
The refractive index of the glass slab is: