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Illustration 34.2: Fiber Optics

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When you carry on a telephone conversation or watch cable television you are likely utilizing fiber optic technology to transmit and receive information. A fiber optic cable provides a less expensive, higher capacity alternative to copper wire with less signal degradation. You may think of fiber optics as being high tech, but the physics behind it is actually quite simple. Restart.

When light is incident on a medium of lower index of refraction at an angle greater than the critical angle, all of the light will be reflected. In the animation, a source of parallel rays of light is embedded in a medium of higher index of refraction than its surroundings. When the animation begins, the light rays strike the interface at an angle less than the critical angle for these two substances. Adjust the angle of the rays by clicking on the beam and then click-dragging the hotspot. At some point the angle is increased beyond the critical angle and the rays are entirely reflected back into the medium.

A fiber optic cable is a thin strand of glass surrounded by a material with an index of refraction less than glass. Light will travel through a fiber optic cable just as the light in the animation was transmitted through the blue region by reflecting off the boundary between the two materials.

Illustration authored by Melissa Dancy.

Physlets were developed at Davidson College and converted from Java to JavaScript using the SwingJS system developed at St. Olaf College.

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