The Nature of Light

How do we see things?

We see some things by the light they give off.

However, . . .
We see most things by the light they reflect.

Our eyes are passive receptors. Our eyes receive light that is already there. Some ancient Greek philosophers thought our eyes sent out "rays" and then we saw because of something those rays did. Other ancient Greek philosophers pointed out that that could not be the case since we do not see in the dark. This idea of "rays" coming from our eyes still shows up in Superman or Superboy cartoons.

Is light a stream of particles -- like tiny bee-bees? Sir Isaac Newton thought so. The sharp shadows we see tend to indicate that it is.

Is light a wave -- like sound or water waves? Christian Huygens, a contemporary of Newton's, thought so. If we look closely enough, as with Young's double slit, we find wave effects.

Actually, we will need both descriptions. And this dual nature of the Universe will be with us throughout our study of atomic and nuclear and particle Physics.

What is the connection between white light and light of different colors?

Table of Contents

Speed of Light

Return to Ch 23, Reflection and Refraction of Light

(c) Doug Davis, 2002; all rights reserved