Reflection, Refraction & Optical Fibers

Objectives / Prerequisites / Technology Requirements

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Overview and Objectives

Optical fibers, also called fiber optics, are currently the primary conduit of digital information. Telephone lines, cable TV lines, and computer networks all take advantage of fibers' capacity to quickly carry large amounts of information. Optical fibers make use of the physics principles of reflection and refraction. This module first explains reflection and refraction, then uses them to explain how optical fibers work.

Upon finishing this module, students should be able to

	State and apply the Law of Reflection.
	Define the index of refraction for a medium, and use it to calculate the speed and wavelength of light in that medium.
	State, explain, and apply Snell's Law.
	Define and calculate the critical angle for the interface of two media.
	Describe the basic structure and types of optical fiber and explain how a fiber is able to guide light.
	Define and calculate characteristics of step-index optical fibers, such as numerical aperture and cut-off angle.

Prerequisites

Before starting this module, students should

	Be familiar with the concepts of wavelength, frequency, and wave speed and how they relate to each other. (The Physics Classroom Overview)
	Be comfortable performing basic algebraic operations. ( Algebra.com [Click on 'Lesson' to get a quick overview])
	Understand geometry and trigonometry as applied to right triangles. (Wolfram Geometry and Trigonometry)
	Have familiarity with metric units of length and metric prefixes. (Metric Units and Conversions)

Technology Requirements

In order to use this module, your browser should

	Recognize Unicode Greek letters: αβγ should be alpha, beta, and gamma. (This will not work on older browsers such as Netscape 4.) If you have difficulty viewing these, we have some older versions of materials available that use Symbol font for Greek letters: abg .
	Have the Shockwave plugin. (Want to check? This page contains a Shockwave animation of refraction.) (Download Shockwave)
	Display animated gifs. (Want to check? This page contains an animated gif of reflection.)
	Recognize Bookman Old Style and Comic Sans MS fonts (these are Microsoft fonts and optional - purely aesthetic).

To view the Guest Lecture, you also need

	Internet Explorer on a PC and Windows Media Player. (Apologies to the Mac users and anti-Microsoft purists, but the video is in Microsoft Producer format and won't play in other environments.)
	A reasonably fast connection to the Internet. (Dial-up should work, but the buffering is sketchy and can take a really long time. It can also lead to periodic pauses in the playback. If you are forced to use dial-up, we recommend letting the video download for some time before you play it.

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