Throughout time, people have been fascinated with rainbows. Their arched splashes of color have been the subject of songs and poems, stories and mythology. In the Bible, the rainbow is seen as a sign of God's promises, and most of us are familiar with the legend of the pot of gold at the end of the rainbow. To unlock the rainbow's secrets, let's explore how water and light work together to produce a colorful work of art.

What makes rainbows so mysterious is this simple but often puzzling fact: Rainbows are light. You can't touch them. You can't reach around behind them. They exist only in the eyes and sometimes the photographs of the people who see them.

Light, or more specifically visible light, includes every color we can see, with violets and blues on one end of the spectrum and oranges and reds at the other end. A rainbow is visible light broken into what we see as seven colors: red, orange, yellow, green, blue, indigo and violet.

What Does It Take?

Three things must happen for you to see a rainbow's colors. First, the sun must be shining. Second, the sun must be behind you, and third, there must be water drops in the air in front of you. Sunlight shines into the water drops, which act as tiny prisms that bend or "refract" the light and separate it into colors.

Actually, the rays of light bend twice. As they enter the drops, the rays of light bend, then reflect off the back of the drops. Then they bend again, this time while exiting the drops. That's when the light appears before our eyes.

Each drop reflects only one color of light, so there must be many water drops to make a full rainbow. You'll see the brightest rainbows when the water drops are large, usually right after a rain shower.

The rainbow is circular because when a raindrop bends light, the light exits the raindrop at an angle 40 to 42 degrees away from the angle it entered the raindrop.

The violets and blues bend at a 40-degree angle, and the oranges and reds bend at a 42-degree angle. As a result, the only beams of light you see are from raindrops that are 40 to 42 degrees away from the shadow of your head. This gives the rainbow its curved appearance.

Full Circle Bows

In the song "Moon River," Georgia songwriter Johnny Mercer wrote, "We're after the same rainbow's end." Actually, though, rainbows have no end. We usually don't see the full circle because the horizon of the Earth is in the way.

But if the sun is very low in the sky, either just before sunset or just after sunrise, we can see a half circle. The higher the sun is in the sky, the less we see of the rainbow.

The only way to see the full circle of a rainbow in the sky is to be above the raindrops and have the sun behind you. You would have to look down on the drops from an airplane.

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©Copyright  2003 Nick Walker/Small Gate Media