BACKGROUND:
Lasers excite
children as well as adults. Lasers are used in the check out stand at
the grocery store, in surgery, and in measurement. However, many people
do not know what lasers are and how they operate. In this activity,
students are introduced to lasers by reviewing light and going over the
properties of light that help lasers work. In lab, students will look at
lasers more closely.
Lasers are basically
excited light waves. Light is a component of the electromagnetic wave
spectrum. The name itself stands for Light Amplification
by Stimulated Emission of Radiation. Students
must first understand two terms: coherent and incoherent light. Light
emitted by normal means such as a flashlight or a bulb, is incoherent or
the photons of the many wave frequencies of light are oscillating in
different directions. It is not a stream of light. Coherent light is a
beam of photons (almost like particles of light waves) that have the
same frequency and are all at the same frequency. Only a beam of laser
light will not spread and diffuse. In lasers, waves are identical and in
phase, which produces a beam of coherent light. There are many types of
lasers that use gases such as helium, neon, argon, and carbon dioxide.
Lasers also use semiconductors (Galiodium and Arsenic), solid-state
material (ruby, glass), and even chemicals (hydrofluoric acid) in their
operation.
With the cavity of the laser the beam
of light is reflected back and forth along the central tube, until the
waves of light become coherent.
