Defining Light
The Fundamentals
Let There Be Light!
Lesson 1: What Is Light?
- Defining Light
- The Source of Light
- The Anatomy of Light
In this lesson, you will learn what light is, where it comes from, and why it becomes a spectrum when it’s exposed to a prism.
Defining Light
You know it when you see it, or when you don’t. But ask any two people to define light, and unless they’re schooled in Physics, you’ll probably get some really basic answers, as in “It’s that thing that comes from the sun and makes everything, you know…not dark”. But like everything in Nature, light has a composition. It has a structure, an anatomy that can be broken down into parts. And it matters because without light, we would have no way to perceive color.
The Source of Light
Light doesn’t just come out of nowhere. All light has a source. Some sources of light are artificial, like lamps and spotlights. But the biggest natural light source known to our species is “Sol”…the technical name for our Sun. We get the bulk of our light from the Sun. We call that natural lighting “ambient” light. Ambient light is the light that’s visible when all artificial sources of light are turned off.
Most of us learned in school that light travels travels really fast at 186,000 miles per second. But exactly HOW does it travel? Light “radiates”, traveling away from its source through space. Light travels in the form of beams that we call “rays”. It doesn’t bend or turn corners. Light travels in a straight line. But if we could take an X-Ray of light, what would it look like? Well, it looks like a spectrum.
The Anatomy of Light
We use a prism to act as our X-Ray. Before we came up with that device, the only way we even knew there was a spectrum was because Nature provided us with the atmospheric conditions required to see a rainbow. The prism gave us our first controlled look at the anatomy of light. Light may look white to the naked eye, but the prism shows us what light really looks like…on the inside. We call that arrangement of color a Spectrum.
This spectral view of light tells us all kinds of things about its anatomy. We call this rainbow the “visible” spectrum…the portion of the spectrum that can actually be perceived by the human eye. The prism shows us the visible spectrum when we aim it at the sun and let natural light shine through it. It isn’t the full spectrum. The “invisible” spectrum includes ultraviolet and infrared light, which the naked eye cannot perceive but it’s very definitely there. The visible spectrum also doesn’t show us all the colors the human eye can perceive. That’s because some colors are are created by mixing. We’ll talk more about this when we get into the subject of primary, secondary, and tertiary colors.