What happens when you dangle your feet in the pool? Or when you place a pencil in a glass of water? Does the object seem bent at the surface of the water?

This phenomenon is due to the bending, or refraction, of light at the interface between the water and the air. Notice that the words refraction and reflection are very similar but have two completely different meanings.

Refraction occurs when light passes into a transparent material.
Reflection occurs when light bounces off an opaque material.

The tricky part of it is that we can have both things happening at the same time, as we will soon discover.

This is an image of a laser beam being refracted at a water surface. Note the laser in the upper left corner of the picture. What do you think would happen to the refracted part of the beam if we changed the angle at which the laser beam is hitting the surface of the water?

Read more about refraction in the reading supplement.

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