The Science of Light (Part 1)

The eye responds to light. Every object viewed is seen with light–either the light emitted by the object or light that is reflected from it. But what is light–that mysterious glowing stuff that gushes forth in infinite color and variety from the sun, from light bulbs, from candles, fireflies and fireworks? The question has troubled man for centuries.

The Greeks pondered it and arrived at several conclusions. The Pythagorean school assumed that every visible object emits a steady stream of particles. Aristotle, on the other hand, concluded that light travels in something like waves.

Even though these ideas were gradually modified as man began to study light with more sophisticated equipment some 20 centuries later, the essence of the dispute established by the Greeks remained. One point of view held that light is wavelike in nature, that it is energy gliding through space the way ripples spread across the surface of a still pond. Another faction argued that light must be a flight of particles–like drops of water shooting in a stream from a nozzle. At times, one view prevailed; at times, the other. Only in the first half of the 20th Century was something like a comprehensive answer found. And oddly enough both theories turned out to be right.

To identify anything–solid, liquid, gas or pure energy–scientists study its properties. Using this approach, the ancient Greeks discovered that light travels in straight lines. The second important discovery about light was made by Hero of Alexandria. Experimenting with mirrors, Hero noticed that any beam of light that was angled in toward a mirror would bounce off again at an equal angle. This made possible the following fundamental rule: the angle of incidence (or striking) and the angle of reflection (bouncing off) are always equal. Although many thinkers continued to reflect on the nature of light, progress was slow until early in the 17th Century.


Life Science Library - Light and Vision