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Measure the Width of a Hair - With a Laser!

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Light is a Particle!

Do you have a laser? Do you have a roll of duct tape that's a really, really bright pink? If so, you can explore the exciting world of quantum physics by demonstrating the particle nature of light!

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

Joanna and Steve: Just science!

Joanna: Hi! I'm Joanna!

Steve: And I'm Steve!

Joanna: If you have a laser, and you know how to use it safely, try this.

Find something that's really bright pink and shine the laser on it.

If you use a red laser, you'll get a red dot, just like you'd might expect.

If you use a green laser, however, you'll get an orange dot.

This isn't a trick and the laser isn't suddenly changing colors. Believe it or not, this shows us that light behaves like a particle!

Steve: A particle of light is called a photon and a photon's energy is related to it's wavelength. The shorter the wavelength, the greater the energy.

All these things contain a fluorescent dye and red light just isn't energetic enough to activate it. That's why there's no change.

Now, we have no shortage of laser pointers, but using more of them doesn't help. Every photon of red light contains too little energy to activate the dye. Using more of them just makes a brighter red spot.

Joanna: Green light has a shorter wavelength than red light, so green photons are more energetic than red ones. They have enough energy to activate the dye. The fluorescence is what causes the orange color.

The amount of green light doesn't matter, either. Any amount of green light will activate the dye because every green photon has enough energy to do so.

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

Steve: So, light is a particle... that has a wavelength?

Joanna: Yep!

Steve: Doesn't that seem strange?

Joanna: It's the wave/particle duality! What can you do?

Steve: I don't know.

Ooh! I can get that green dot!

One day, my pretty... One day...

But not today...

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