Reflection and Refraction of Light: Refracted Light

The video explains how certain visual phenomena, such as the sun appearing oval at dusk or dawn, mountain streams seeming shallower, and roads shimmering in the desert, are caused by the refraction of light. Refraction occurs when light waves pass from one substance to another, changing velocity and bending the light. The degree of bending is determined by the index of refraction, which varies between substances. For example, light travels 33% slower in water than in a vacuum, as indicated by water's refraction index of 1.33.

How does the index of refraction relate to the speed of light in different substances?

What is the index of refraction for water, and how does it compare to that of a vacuum?