If the wavelength of light in air is $4200\, \mathring A$,what will be the wavelength of light in water $(\mu = 4/3)$ in $\mathring A$?

$A$ ray of light is incident at an angle $i$ on a glass slab of refractive index $\mu$. The angle between the reflected and refracted light is $90^{\circ}$. Then, the relationship between $i$ and $\mu$ is

$A$ 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:

An electromagnetic wave,whose wave normal makes an angle of $45^{\circ}$ with the vertical,travelling in air strikes a horizontal liquid surface. While travelling through the liquid it gets deviated through $15^{\circ}$. What is the speed of the electromagnetic wave in the liquid,if the speed of electromagnetic wave in air is $3 \times 10^8 \ m/s$? $(\sin 30^{\circ} = 0.5, \sin 45^{\circ} = \frac{1}{\sqrt{2}})$

The speed of light in a medium of refractive index $1.25$ is . . . . . . .
(Speed of light in vacuum is $3 \times 10^{8} \,m \,s^{-1}$)

The phase difference between the incident wave and the reflected wave is $180^o$ when a light ray: