How is the refractive index of a material related to the speed of light in it?

The refractive index of diamond is 2.42. What is the meaning of this statement in relation to the speed of light?

If the refractive index for light going from air to diamond be 2.42, what will be the refractive index for light going from diamond to air?

State whether it is true or not:

When a ray of light goes from air into a clear material, you see the ray bend. How much the ray bends is determined by the Refractive index of the material.

Give three examples of materials that refract light rays. What happens to the speed of light rays when they enter these materials?