What is the importance of total internal reflection?

What kind of lever is a human arm? How fast does liquid travel up a straw? What is the minimum standoff distance when applying water to an energized electric source? Why are you more likely to see a mirage on a hot day than on a mild day? Are space and time are absolute? Is it necessary to have matter at the center of mass? Can the energy of a body can change only in small discrete units? What does tension between opposing forces mean? Why heater coil glow but supply wire not glow? What is light object? What are 2 examples remain at rest? What is a pointing device used by laying the palm of the hand over it and moving it across the surface of a pad that provides traction for a rolling ball on its bottom.? What happens if the buoyant force on an object is greater than the weight of the object? How is a shadow affacted by the brightness of the light source? Is wind constructive or destructive? What happen when an object have no atoms? What is a fixed object used to determine the movement of another object? What is 0.2 kg? Is a dental mirror concave or convex? A collision occurs every?

What is the importance of total internal reflection?