Total+Internal+Reflection

=//Total Internal Reflection//=

**Theory**
If light moves from a denser medium to a less dense medium, it will refract away from the normal. Since the angle of refraction is larger than the angle of incidence, it is possible to have an angle of refraction of 90 degrees. This is called **total internal reflection**. The light cannot exit the medium and is effectively “trapped” in the denser medium. The angle of incidence that leads to a 90 degree angle of refraction is called the **critical angle**.

**Calculations**
Total internal reflection can be calculated using Snell’s Law: Where n1= index of refraction for medium 1 n2= index of refraction for medium 2 q1= angle of incidence q2= angle of refraction

Set q2 to 90 degrees. The sin of 90 degrees is one. Substitute all other known values into the equation and solve for the unknown.

**Uses**
This phenomenon can be seen in a real life scenario at the pool. If you are just below the water and look to the surface, the water surface will appear mirror-like because total internal reflection is occurring and trapping the light waves. This also gives well-cut diamonds their shine and sparkle. Fiber optic cables also work on this principle.

**Applet**
These principles can be tested using this applet: []

//References//

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