Read

Read "Total Internal Reflection" on pages 672-673 of the textbook for more information on critical angles.


Read
Read "Total Internal Reflection" on pages 672-673 of the textbook for more information on critical angles.

 

Try This
Manipulate Snell's Law to give an expression that will solve for the critical angle then calculate the critical angle for a water-air interface. n1n2=sinθcriticalsin 90° Verify your answer using the Refraction simulation. (48.8 o )


Applications of Total Internal Reflection: Light Pipes and Mirages

 

Light pipes (and fibre optics) are very common in medicine, science, and industry.  Light pipes work by trapping light using total internal reflection.  You can create a light pipe using a long Lucite rod.  Lucite is a common type of plastic that has a relatively high index of refraction at 1.49.   Check out this video on light pipes.

 

Use the refraction simulation to build a light pipe similar to that shown here. Position the laser pointer in the Lucite layer ( n  = 1.49) and point it so that total internal reflection occurs.  Explain how it traps the light.  If you submerged the Lucite light pipe in water, would that improve or degrade its performance?


A common mirage (optical effect) is the wet appearance of a prairie road or field on a hot summer day.  A mirage is formed when the air layer above the ground is very hot and has a slightly lower refractive index than the cooler air just above it.  Such a refractive index gradient is illustrated by the following ray diagram and observed in the photo on the right.  The wet pond mirage is refracted light from the sky.

Image by Norbert Schmitz from Pixabay

  



 

Mirage conditions can be set up in the laboratory as well - look up some videos on mirages like this one:

   Can you produce a mirage?  Review "Figure 13.45" on page 667 of your textbook.