# Image Conduit

##### Concepts Shown:

transparent materials, optical wave guides, critical angle, total internal reflection.

##### Equipment:

image conduit 3.5" long, cards or pictures with sharp, bright images Cost: \$33 This image conduit was obtained from: American Science & Surplus (708) 982-0870 Item # 22189

##### Procedure:

Setup:
Simply order the glass from American Scientific and sleect images to transmit (this is mainly done by trial and error, as to what you think are the most dramatic images).

Presentation:

1) Set optical glass on any flat surface containing an image and look at the top of the glass.
2) Pass around so students have an opportunity to look at various images through the conduit.
3) Discuss scientific principles and applications.

Note:
Show along with fiber optic cable for a more thorough presentation.

##### References:

This experiment shows the basic principles behind fiber optics. Light is simply a form of electromagnetic wave, the same as a radio wave, except with a different wavelength. As with radio waves, signals can be sent on these waves by simply varying the frequency. The problem in the past with using light as the medium for transmitting a signal was that it was extremely difficult to guide it along a path. However, today through the sue of transparent materials, engieers have developed cables which transmit or signals across great distance with extremely little signal loss and requiring low amounts of power. This is due to the critical angle of the fiber optic material and total internal reflection. If the light traveling within a fiber bounces off the all at an angle less than the critical angle, the signal will remain inside the cable. This is shown by the equation: n1/n2 = sin 90/sin phi(2) where n1 is the index of the material clad around the waveguide, n2 is the index of refraction of the material, phi(2) is the critical angle of the wave guiding material. Below this angle the cable has total internal reflection - no signal is allowed to escape if the material is not blemished. [eq]. The fibers in this particular demo are nanometers thick but are still able to transmit an exact signal from one end to the other. Fiber optic materials have become so refined that if you made a window pane seven miles thick out the glass used in today's telecommunication fibers, you would be able to see right through it, all seven miles. Using these cables, signals can be sent anywhere ini the world with relative ease. Although these particular cables are made out of a rigid transparent material, there are several materials taht are flexible making the applications even more practical. Besides just telecommunication, in medicine for instance, they can transmit an image from deep inside the body to the outside where doctors can more easily examine it. In the past, this would only have been possible with a bulky camera that does not like to squeeze deep ito the body.

##### Author:
Tyler vanHouwelingen