Joan Cartan-Hansen, Host: Light and color all start with the sun, but when it comes to light and color, there's more than the eye can see.

Let me illuminate you.

(MUSIC) Student: What is light?

Cartan-Hansen: Light comes from the Sun.

And everything on earth needs light to live.

Student: But that doesn't tell me what light is?

Cartan-Hansen: Well okay.

To understand light, you have to get pretty close.

Student: Whoa!

(Wooshing Sound Effect) Cartan-Hansen: Light is energy.

It's made up of tiny particles known as photons.

Light moves in waves like sound, but much faster.

Sound waves travel at 750 miles per hour while light travels at over 6.5 million miles per hour.

Light travels in a straight line but it can bounce.

That's known as reflection.

You see yourself in a mirror because the light is being reflected back at you.

Light can also bend.

When you see flowers in a vase, the stems in the water could be slightly off.

That's because light traveling through the water and through the glass is getting bent.

That's known as refraction.

It happens because light travels at slightly different speeds through different materials.

Some telescopes use refracting lenses to capture light so we can see far into the universe.

The waves of light from the sun or, as we call it-white light, is actually made up of a bunch of different colors.

Isaac Newton discovered that fact when he directed sunlight through a prism.

When you shine light through a prism, it breaks up the white light into its colorful parts.

Red, orange, yellow, green, blue, indigo, and violet.

Student: Hey, that's a rainbow!

Cartan-Hansen: That's right.

We see rainbows in the sky because water droplets in the air act like tiny prisms and split the sunlight before it reaches our eyes.

Now each color has its own wavelength.

Student: Wait a minute.

What is a wavelength?

Cartan-Hansen: Well light, like sound, travels in waves.

Scientists measure the distance between the high spot or the crest of one wave to the crest of the next wave.

The distance between the two spots is calling the wavelength.

Of the colors, red has the longest wavelength and violet has the shortest.

We see things in color because our eyes perceive each different wavelength of light as a different color.

For example, when light shines on a rose, the rose absorbs all the colors of light except, in this case, red.

Those red waves of light are reflected to your eye and special cells in the back of your eyeball tell your brain that the rose is red.

Student: Cool.

Cartan-Hansen: But what we see is just part of the story of light.

There are lots of other light waves.

Scientists categorize all wavelengths of light in the universe on the electromagnetic spectrum.

Radio waves are on the low end of the spectrum.

Their wavelengths are very tall.

Next are microwaves, infrared waves and then the visible waves, those are the white light that humans can see.

After that are ultraviolet waves, x-rays, and gamma rays.

While we can't see infrared waves, we can feel the heat that they produce.

And if you don't use sunscreen when you are out of doors, ultraviolet waves can give you a sunburn.

In general, we're lucky here on earth.

Our atmosphere protects us from a lot of the damaging waves of light on the electromagnetic spectrum.

So, what is light?

Light is energy from the Sun and stars.

And the white light we see is made up of a rainbow of colorful waves of different wavelengths.

Light and color, you don't have one without the other.

If you want to learn more about light and color, check out the Science Trek website.

You'll find it at Science Trek dot org.

(MUSIC) ANNOUNCER: Presentation of Science Trek on Idaho Public Television is made possible through the generous support of the Laura Moore Cunningham Foundation, committed to fulfilling the Moore and Bettis family legacy of building the great state of Idaho; By the Idaho National Laboratory, mentoring talent and finding solutions for energy and security challenges; By the Friends of Idaho Public Television and by the Corporation for Public Broadcasting.