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Lights on Pipes! An Experiment with Light and Heat

Three pipes with three different surfaces are blasted with light. Which pipe will heat up the most? Download the worksheet and conduct the experiment with us!

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

Joanna and Steve: Just science!

Joanna: Hi! I'm Joanna!

Steve: And I'm Steve!

Joanna: Today, we're going to an experiment with light and heat. It's simple enough that you can make your own set-up and do this at home, or you can download a worksheet from our website and follow along with us.

Basically, we're going to be shining lights on pipes to see which one warms up the most!

Steve: The pipes are the same, except for their surfaces. This one is painted white, this one is painted black, and this one is wrapped with some stuff called aluminized mylar. Which, if you've ever had one of those shiny helium balloons, it's that stuff.

Now, we've done our best to make sure that everything else the same. The size of the pipes. The brightness of the lights. The amount of time the lights are on. The only thing we've changed on purpose is the surface of the pipes.

Joanna: Before we begin, form a hypothesis. Which one do you think will warm up the most? Remember, when light strikes something, it can either reflect off of it, pass through it or be absorbed by it. If we want the pipe to warm up, if we want it to gain energy, which of these things has to happen?

Steve: We're going to shine the lights on the pipes for four minutes and we'll record the temperature every thirty seconds. Go ahead and get the initial readings now.

We'll keep time on the screen and we'll even freeze the video for a bit when it's time so you can get the readings.

Joanna: So, if you're ready...

3... 2.... 1... Start!

Joanna: Even before we graph the data, it's pretty obvious that the black pipe warmed up the most. And, that should make sense. None of the pipes transmit light, so they either reflect the light or they absorb it. The black pipe reflects the least amount, so it must absorb the most light. The more energy it absorbs, the warmer it gets.

Steve: Also, you also might have noticed that, initially, the white pipe warms up faster than the black pipe. I have no idea why that is, but finding out could make for an interesting science fair project.

Joanna: Thanks for watching! I hope you'll join us again soon for another experiment!

Steve: So, think I'm a little old to enter a science fair?

Joanna: No!

Steve: Oh, good!

Joanna: I think you're a LOT old to enter a science fair!

Steve: Oh, Joanna!

Joanna: Sorry!

Steve: Why?!

If you are concerned that the placement of the lights resulted in uneven lighting, a second trial, conducted in full sunlight, is available.

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