Manipulatives for the Heat Vision Camera

These things are all basically the same thing: light, the energy that cooks food in microwaves, radio waves, x-ray radiation, and the infrared signal that comes out of your remote control. They are all part of the electromagnetic spectrum, a hierarchy of electromagnetic radiation divided into categories by wavelength.

So, our eyes are very good at detecting electromagnetic radiation in a certain spectrum of wavelengths: what we call visible light. Just slightly wider wavelengths produce a light that we cannot see: infrared light. That's the "light" given off by molecules when they vibrate. But you know this as heat. Here at the Discovery Center, we have a really nifty camera that detects heat, and displays it as a colorful image. By comparing the colors, you can determine what's hot, and what's not.

Check out these links if you want to know more about the electromagnetic spectrum, or infrared spectroscopy.

I fabricated a couple of interesting manipulatives for interacting with our heat vision camera.

The first is made out of acrylic sheet, the generic name for the brand Plexiglas®, which has some interesting properties. It transfers visible light, so you can see through it like glass. However, it absorbs the infrared spectrum. So, heat does not transfer through the sheet, at least not in the wavelengths we usually encounter with warm bodies and room temperature objects. So, an infrared camera cannot see through acrylic. Check out this video to see what I mean:

Now, the reason acrylic does not transmit infrared radiation is due to the arrangement of its molecules and the vibration of those molecules. It's interesting to think about a "clear" material absorbing infrared radiation, because that's exactly what happens in Earth's atmosphere. The sun casts its infrared radiation upon the land and oceans on Earth, and much of it is reflected back into space. But, not before being absorbed by the gasses in the atmosphere on the incoming and outgoing trip. This is what keeps the planet warm. However, the density of those atmospheric gasses is finely balanced. Nitrogen, for example, makes up most of the atmosphere, yet transmits heat without absorbing it. Humans are contributing more and more heat-absorbing carbon dioxide to the atmosphere by burning fossil fuels and forests. The result is a hotter land temperature, as those gasses radiate heat back toward us. That's global warming.

(Meanwhile, back at the museum...)

I put some text around the edge of this manipulative to help the visitors understand a little about why it works. I applied this text by tracing printed words onto the acrylic with an engraving tool. It was very time-consuming! It says "This material transmits visible light, but absorbs the infrared spectrum."

The other manipulative is a rectangular paddle with a unique material stretched across the interior.

 This material blocks almost all visible light, so you cannot see through it at all. However, it is almost completely invisible in front of a heat-vision camera, because it transfers almost all infrared light without absorbing much at all. The thin, black, opaque material stretched across the open interior of the paddle is something you're very familiar with, but I bet you've never played with it in front of an infrared camera.

I'm not telling you what it is. You have to come down to the Discovery Center and see for yourself.