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Video Transcript

(7.7s) Hi, I'm Becca Emerich, the Educational Program Manager at Edmund Scientific, the outreach division of Edmund Optics. Today, we're going to talk about total internal reflection, or TIR.

When light travels from one medium to another, for example, from water to air, some of the light is always refracted, and some of the light is always reflected. When you hit a certain angle, called the critical angle, all of the light is reflected. The total amount of light is reflected, and that's called total internal reflection.

Let's take a look at total internal reflection. When I shine this laser into the fish tank at the critical angle, TIR takes place. The ray of light reflects off of the top of the water and down to the bottom of the fish tank. It then reflects off of the bottom of the fish tank back up. Theoretically, TIR would go on forever if the fish tank went on forever.

(10.3s) I have punctured a hole in this bottle of water. When I point the laser through the hole and into the stream, TIR takes place and the beam of light travels with the stream of water. The light is bouncing or reflecting back and forth through the stream of water, allowing the light to travel with the stream. Fiber optics work because of total internal reflection. When I shine the laser beam through the fiber optic, the light reflects back and forth through the solid glass tube until it reaches the end of the tube. Information can be transmitted in this way.

Good scientists and engineers always test out scientific theories for themselves. To obtain lab instructions so that you can try these demonstrations at home or at school, click on the following link. Thanks for watching. (6.1s)

Total Internal Reflection

Join Rebecca Emerich, Educational Outreach Manager, and see "Total Internal Reflection" in action with fun experiments you can try at home or at school! To learn more about Edmund Scientific's educational resources, including labs and inspiration kits, please visit www.edmundscientific.com.