In the figure shown,the angle made by the light ray with the normal in the medium of refractive index $\sqrt{2}$ is.....$^o$

$A$ ray of light is incident on the surface of separation of a medium at an angle of $45^\circ$ and is refracted in the medium at an angle of $30^\circ$. What will be the velocity of light in the medium?

Explain rarer and denser medium.

$A$ beam of monochromatic light is refracted from vacuum into a medium of refractive index $1.5$. The wavelength of refracted light will be

$A$ tank is filled with benzene to a height of $120 \,mm$. The apparent depth of a needle lying at the bottom of the tank is measured by a microscope to be $80 \,mm$. The refractive index of benzene is: (in $.5$)

Two light beams fall on a transparent material block at points $1$ and $2$ with angles $\theta_1$ and $\theta_2$ respectively,as shown in the figure. After refraction,the beams intersect at point $3$,which is exactly on the interface at the other end of the block. Given: the distance between $1$ and $2$ is $d = 4\sqrt{3} \text{ cm}$ and $\theta_1 = \theta_2 = \cos^{-1}\left(\frac{n_2}{2n_1}\right)$,where $n_2$ is the refractive index of the block and $n_1$ is the refractive index of the outside medium $(n_2 > n_1)$. Find the thickness of the block in $\text{cm}$.