(bright upbeat music) - Hi guys.

Thanks for joining us at GPB Education for this fun exploration of color.

My name is Tracy and my favorite color is green.

I love being outside where there are lots of green things.

I like green plants that grow outside like Moss and Ferns and Trees, I like green fruits and vegetables that grow outside like Cucumbers and green Apples and Grapes.

I even like green animals that live outside like Turtles and Snakes and Frogs.

What is your favorite color?

I know it's really hard to choose just one, there are so many to pick from.

In fact, scientists think there are 18 decillion colors in the universe.

Decillion is a really big number.

It has 33 zeros.

Wow!

But what is color anyway?

Where does it come from?

Why is it so important to us?

A lot of people try to answer this question, what is color?

For a video contest, 27,000 kids from 19 different countries voted on all the videos, and this video was their favorite.

It's from a PBS series called physics girl.

Let's watch it.

(energetic music) - Hey you, what is color?

Is it this red light?

Is it this blue ocean?

Is it these egglettes?

Yeah.

They're not even white.

What's up with that?

Anyway, there are many more mysterious aspects of color that we're going to figure out.

But first, you have to be color.

- [Background Voice] Huh!

- Just pretend that you are color.

(orchestral music) You are color.

Yeah, you.

In your journey through the world as color, you start out as a wavelength of light.

In order to find out what color you are, we must look at your wavelength.

Light is a wave that travels through space and like any wave, it has what's called a Wavelength.

That's just the length of one peak to the next peak.

Different colors are simply different wavelengths of light.

For example, red has a longer wavelength than green which has a longer wavelength than blue.

So, let's take a look at your length.

Well, well it looks like you're all the colors of light which means you're actually white light which is just a combination of all the other colors of light.

Now, light moves super fast so you better get, oh!

good job.

As you move along, you bump into an object.

(mourns with pain) You didn't fall that hard.

Hey look!

You're red.

Oh, you're wondering what happened to all the other colors.

They were absorbed into the car.

Oh geez!

Not like that.

When light hits a car, some colors are reflected and some are absorbed into the paint based on the structure of molecules or chemicals in the paint.

In the case of this red car, the molecules absorb every other color, orange, yellow green, blue, indigo, and violet and everything in between.

But red is reflected.

So far, we've uncovered two mysteries of light.

White light is actually all the colors of light and a red car absorbs everything but red.

Well, it gets even more mysterious once you reach an eyeball.

Up, you go.

You are now light with a red wavelength and you're headed straight for an eye ball.

(glass shutters) You've passed through the lens of an eye.

See all those things around you?

Those are rods and cones.

Inside an eyeball are what's called photo receptor cells which is just a super fancy word for a cell that is sensitive to light.

It can take light and turn it into a signal that is sent to the brain.

Photo receptor cells are what actually allow you to see.

Cones are the cells in your eyes that perceive different colors.

So you can think of them like colorful ice cream cones.

Rods are used more for night vision.

So any color sense by a rod just looks like some shade of black and white just like a rod.

You are about to be absorbed by these cells.

But wait, I must warn you something might go wrong in the process.

First, let's figure out how we see red.

When we see red, we're not actually seeing red.

- [Background Voice] Huh!

- Remember those cones in your eyes, there are three different types of them, red, green, and blue cones.

They are each sensitive to different colors so if you shine red light on them, the red cone will respond a lot, the green color, a little less and the blue cone almost none at all.

That combined response is what tells us it's red light.

Blue light would be perceived more like this.

If any of these types of cones is not working properly, you perceive color differently.

This is how one type of color-blindness happens.

Luckily, this is a good eye so you are absorbed properly and are now a signal on your way to the brain.

At this point, you are still color though now you're a signal as well, but not for long.

Soon the brain will receive the signal and perceive that the eyeballs saw the color red.

So now you are a perception.

I know this is all very confusing.

So far, you are a light Wave a reflection, a signal and now you are a perception.

But you're still just color.

Didn't I tell you color was a mystery?

Whether color is a wavelength of light, a reflection, a signal or a perception, I think I prefer my world with color.

- That's pretty cool, isn't it?

So even though we can't see all the colors around us with our eyes, they're there.

But today we're going to be building a tool that will help us see all the hidden colors.

It's called a Spectroscope.

Spectro means band of colors and scope is a tool that helps us see.

So a spectroscope helps us see the band of colors in white light.

Here's what we'll need to build our Spectroscope.

You should be able to find these materials just around your house.

First of all, we'll need a paper tube.

You can find these paper tubes inside paper towels when you're done with them.

But I got this one from wrapping paper and the ones inside wrapping paper tubes are a little bit harder.

So if you can find one of those, that'd be great.

You'll also need something called a Compact Disc or CD.

We used to use these a lot in the past and we don't use them as much anymore so your parents or even grandparents may have some old ones lying around the house that they don't use anymore.

The third thing you'll need is some aluminum foil.

So you'll see, I have two different squares of aluminum foil that I've cut out.

They're about the size of my face.

And so you can cut out two of those and you'll also need two strips of aluminum foil.

These are long rectangles.

You can maybe take another square and cut it into strips and you'll use that as well.

And then the last materials that you'll need are to help put things together and those are tape and scissors.

So I'll give you a few minutes to look around the house and get those materials together.

Then when you come back, we'll build our Spectroscope.

All right everybody.

Now that we have our materials together, it's time to build our Spectroscope.

We're gonna start with the CD.

You see this is an old Compact Disc from my house.

It says CD right here and make sure you find a CD and not a DVD.

They look very similar but only the CD will work for our experiment.

We're also gonna need a sharp tool such as this pair of scissors.

And what we're gonna do is just scratch a little line in the top coating.

There's a coating of paint on top of the CD.

And we wanna scratch it away with our sharp tool so we can get to that clear diffraction grading that's underneath.

You can buy diffraction gradings online too but it's much better just to recycle an old CD that we have in our home.

Right?

So now that I've cut a little scratch in that paint, I'm gonna use a piece of tape and I'm just gonna use scotch tape, but any tape will work.

I'm gonna pull off a piece of tape and I'm gonna press it against that line I made in the CD and press it down.

So I'm trying to get ahold of that tape so I can peel it away and get ahold of the paint so I can peel it away.

And you'll see what happens is just like magic.

I have started to peel the paint from the top of the CD so I can expose that clear diffraction grading that is underneath.

And you can see the diffraction grading is already doing its work.

It is defracting the white light from the lamp shining on it and turning it into a spectrum of colors.

So now that we've exposed our diffraction grading, we're gonna take a larger piece of sci, a larger pair of scissors like some kitchen sheers and we're gonna cut out a little square or a couple of squares from this area that we're gonna use in our Spectroscope.

Once you cut them out, they're gonna look something like this you just have a couple so that you have one that you're gonna use and one that's a backup.

And you'll see these two are already doing their work starting to diffract that white light into a spectrum.

You wanna make sure that the little square that you cut is smaller than the opening of the tube because it's gonna go over that opening.

So make sure that it fits inside the tube.

So let's put that aside and now we're gonna bring out one of our aluminum foil squares that we cut out earlier.

And we're going to cut, we're gonna fold it in half linked wise so it just makes a nice little rectangle and then we're gonna fold it again.

And this time it's gonna be folded into a smaller square like that and where the folds come together in that corner.

So this particular corner has all the folds right there.

We're gonna take our scissors and we're just gonna snip out a little, snip out the corner.

And you'll see once we've done that, then we can open it back up into its original square and in the middle, there's a little hole now.

And that hole is the hole we'll be using to look through into our Spectroscope.

So we're gonna take the piece of diffraction grading that we cut out of the CD and we're gonna place it over top of the hole.

And I'm trying not to touch it 'cause I don't want too many fingerprints on it so I placed it over the hole.

Now we take another piece of tape and I'm gonna tape it in place.

And I wanna make sure the tape doesn't cover the hole but it's just on the edge of the square to hold it in place.

So a couple pieces of tape, maybe two or four just to hold it in place.

You can see once again, there's the diffraction happening.

Then I'm gonna take my tube, my paper tube from the wrapping paper and I'm just gonna put it over top of that little diffraction grading square and then I'm going to pull the tinfoil up around the tube and squeeze it into place.

And so that makes one end of my Spectroscope.

We'll see right there is the diffraction grading and the hole that I'll be looking through and I've clamped the tinfoil down really tightly to cover that end.

Now I'm gonna take another piece of tape and just pull it off of my tape and I'm gonna tape all this in place so it won't move.

And so now I've taped that end in place.

So one end is complete and now we just have to work on the other end here.

So let's put this aside and pull out our second square of aluminum foil and do the same thing that we did with the last square, we're gonna fold it in half to make a rectangle, fold it in half again to make a smaller square.

Take our scissors and snip out that little corner there and then open it back up into a square.

So this is gonna go on the other end of the tube.

But we need to make this into a slit so that we can really isolate the light that's entering the Spectroscope.

So for that, we're gonna take the two strips of aluminum foil that we cut, remember that and we're gonna fold them in half.

So I'm gonna fold it in half here so it's this really nice, flat crease and the same thing for the other one, fold it in half, it's a really nice flat crease.

Then when we lie in those two creases up next to each other, they make this really clean strip of, clean strip that the light can go through.

And we'll lay these two over top of the hole in my square.

And I want that opening, that strip that the light will come through to be about the width of a coin.

So that works.

And what I wanna do is tape those in place.

This part's a little tricky 'cause they move so easily.

So you wanna take your piece of tape and cap touts on it and get them to stay in place like that.

And make sure your tape doesn't cover the opening again, doesn't cover the slit but just kind of tapes those two strips in place so you have that one little strip, one little split where the light will come through.

Then take your tube again and like we did before, you're gonna put the end over that slit and then pull the tinfoil up around it like that.

Now this time, now we're gonna go ahead and make sure that it, that it's in place, but this time we're not gonna tape it because we wanna make sure that that light is entering correctly.

And so we're gonna adjust it before we make, before we tape it down.

Okay.

So now our Spectroscope is pretty much complete.

Here it is, the tube of paper.

One end has the diffraction grading, we're gonna look through this end.

And then the other end has the slit.

And this is the slit that we're gonna focus at the light so that the light can enter through that little slit.

So I adjusted my desk lamp so the spectrometer is pointing at it and you can see how it works.

The end with the slit is pointed right at the white light and the end with a diffraction grading is pointing at the camera.

So you can see what it look like as if you were looking through it with your eye.

And there is the spectrum, red orange, yellow, green, blue, indigo, violet.

All the colors diffracted from that white light visible now through my Spectroscope, this simple tool that we made together using just tin foil, a paper tube, some tape, an old CD and sources of light.

So guys, thanks for joining GPB Education for this exploration of color.

I hope you had fun, learned a lot and built a really cool Spectroscope that you can use for the rest of the Summer.

You can point your Spectroscope at all different sources of light, lamps and light fixtures, even fire that's in the fireplace or on your gas stove if you're careful.

Just don't point it directly at the sun, that could hurt your eyes.

But you can point it at places where the sun is reflected like white cars or light colored walls or even the sidewalk.

If you'd like to find other fun science and stem projects like this, you can go to www.GPB.PBSlearningmedia.org.

And when you're there, you can set up your own free account where you can search for all different kinds of fun videos, games and other projects like we did together today.

Thanks for participating guys and have a super summer.