If we look closely, we see that there is no refracted part of the beam. All of the laser beam is being reflected at the surface of the water.

This is a phenomenon called total internal reflection. As an example, it occurs when light is traveling through water or glass and hits the surface of the water or glass in such a way as to be reflected back into the water or glass. The "internal" part means that the light beam has been traveling inside some material and is then totally reflected at the surface back into the material.

Some other examples of total internal reflection include gems that sparkle, like diamond: light enters a diamond and because of the properties of the diamond, the light is totally internally reflected many times before it can "escape". In this case, the light is also being dispersed inside the diamond, so we see many beautiful colors when the diamond sparkles.

Another example is an optical fiber which uses total internal reflection to transmit data (light) down the fiber. Every time the light hits the inside wall of the fiber, it is totally reflected and thus propagated down the fiber. To learn more about fiber optics, go to the Fiber Optics Submodule.

Read more about total internal reflection.

How can we harness this elusive spectre called light?

Return to the Total Internal Reflection Page

Submodule 1 Page