Science at Home Videos

Announcer: Frostbite Theater presents... Cold Cuts! No baloney!

Joanna and Steve: Just science!

Joanna: Hi! I'm Joanna!

Steve: And I'm Steve!

Joanna: And this is a 'Science at Home' edition of Frostbite Theater that you can do along with us! Just download the worksheet from our website or you can record your data on a piece of paper!

Steve: Today, we're going to test some different materials to see which are good at blocking ultraviolet light.

Joanna: Just like visible light, ultraviolet light is a form of electromagnetic radiation.

We can't see ultraviolet light, however, because the wavelength is too short. But, just because we can't see something, doesn't mean we can't detect it.

Steve: I'm holding a bunch of UV sensitive beads. They change color as soon as I expose them to the sun's ultraviolet light.

Joanna: We'll be using the beads as our detector.

If a material does a really good job of blocking the ultraviolet light, the beads won't change.

If a material does an okay job of blocking the ultraviolet light, the beads will change some.

And, if the material does a really lousy job of blocking the ultraviolet light, the beads will change a lot.

Steve: And, even though we have different color beads, we want to use one color throughout the experiment.

Right? If we have purple beads and we have yellow beads and we try to compare them, it's hard to tell if the purple one is as purple as the yellow one is yellow. We can avoid that headache by using one color.

And, speaking of headaches to avoid, we want to avoid that. If we do this out here, the sun's ultraviolet light will change the beads as soon as we remove the materials.

So, with the snap of my fingers, and through the magic of editing...

--SNAP!--

We've moved everything inside.

Joanna: We'll cover the beads with a half-gram each of SPF 4 sunscreen and SPF 45 sunblock.

Steve: And with a lens that's suppose to be transparent to ultraviolet light.

Joanna: And a lens that's suppose to be opaque to ultraviolet light.

Steve: A piece of cloth.

Joanna: And a piece of roofing shingle.

We'll also have two sets of control beads. One set will be exposed to the ultraviolet light without any special covering, and the other set won't be exposed to the ultraviolet light at all. That way, we'll know what maximum exposure and zero exposure look like.

Steve: We'll expose the beads to the ultraviolet light for two minutes. We won't tortue you with the real time footage of that, but this is a great place to pause the video if you want to come up with a hypothesis for which materials will block the UV light and which materials won't. Because we're going to show you the results in...

Joanna: 5...

Steve: 4...

Joanna: 3...

Steve: 2...

Joanna: 1!

Steve: Now, if I were doing this, I would say that the non-exposed control beads have a purple-ness value of 1 and the exposed control beads have a purple-ness value of 4 and I would rate the purple-ness of the experimental beads on this 1 to 4 scale.

And, just because I'm using numbers doesn't make this quantitative data. We're judging the purple-ness of the beads. We aren't measuring it with a purple-ness meter. So, it's qualitative data.

Joanna: As an added bonus, did you know that you probably have an infrared detector staring you in the face?

Infrared light is another form of electromagnetic radiation. We can't see it, however, because the wavelength is too long. Even though we can't see it, we use it all the time for things like remotes! Even though I can't see the infrared light... my computer can! Maybe yours can too!

Joanna: Thanks for watching!

I hope you'll join us again soon for another experiment!

Ooh! I know another way we can detect ultraviolet light!

Steve: Really? How?

Joanna: That little bald spot on the top of your head!

Steve: What?!

Joanna: You're going to get sunburned out there!

Steve: This is coming from the person who has to apply SPF 1000 before walking past a window?

Joanna: This is true!

Steve: Awww, man...

You're not wrong, though...

Need to get a hat....