Additional Info

• ID Code: L5-11
• Purpose: Demonstrates total internal reflection of a laser beam in a water jet
• Description:
  

  A clear plastic tank with a plugged spout is elevated above a second, shallower tank. The upper tank is filled with water. A laser is aligned so that it passes through the upper tank and is centered on the spout.

  When the spout is unplugged, the water streams out into the lower tank. Several internal reflections of the laser beam should be visible in the outgoing stream of water, down to the point where it becomes too turbulent to see clearly.

  As the water level in the tank drops, the water flow becomes so slow that the stream bends too sharply and there is no internal reflection, and the laser beam ceases to follow the flow of water.

  Background:

  The laser here is illustrating internal reflection: depending on the index of refraction of the water and the angle the light hits it at, more light can be reflected back and forth within the stream of water than passes through it. At a certain point, it exhibits total internal reflection, where essentially all of the light is traveling along the stream rather than heading straight out the side.

  This demonstration can beneficially be used in combination with demonstrations of fibreoptic technology such as L5-13 or L5-23.

• Availability: Available
• Loc codes: OS2, LS1
• Videos-1: Demonstration video on YouTube