Corpuscular theory of light predicts the speed of light to be

When a light ray enters from air into water, which of the following properties does not change?

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 $\text{cm}$.

$AB$ is a boundary separating two media of different refractive indices. $A$ ray is incident on the boundary and is partially reflected and partially transmitted. Choose the $\text{CORRECT}$ statement.

What are optically denser and optically rarer media?

Draw a figure that illustrates the reflection and refraction of light.