Refraction in Different Media

The refractive index of diamond is $2.42$. What do you mean by this? Calculate the speed of light through diamond.

Will a ray of light deviate towards the normal or away from the normal when it enters from air to diamond obliquely provided the refractive index of the diamond is $2.42$.

In the table the absolute refractive indices of certain transparent media are given.
 
Find out from the table the medium of highest and lowest optical densities.

Separate the given diagrams as no deviation, deviation towards normal and deviation away from normal.

Observe the figure. Light falling on two different media are shown.
Which medium has greater refractive index?

Observe the figure. Light falling on two different media are shown.
Which medium has greater optical density? Why?