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# Light

## Explores visible light, why light appears colored and electromagnetic waves just outside of the visible range.

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Practice Light

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Where's the Remote?

### Where's the Remote?

Credit: Robert Lopez
Source: CK-12 Foundation

Remote controls. You use them all the time to control your electronics, especially the TV. You may not realize how much you depend on them until you misplace them. Then you may spend an hour looking for the remote before you remember that the TV has buttons to control it! As much as you use remotes, do you know how they work?

#### News You Can Use

• A remote control is a device that communicates with another device, such as a TV, using light signals. But it’s not light you can see.
• Credit: David
Source: http://www.flickr.com/photos/brokentaco/4528349058/

Cameras are able to capture infrared light and create some amazing photos [Figure2]

• The signals consist of infrared light, which has wavelengths that are too long to be detected by the human eye.
• Watch this video to learn how a remote control works: http://www.youtube.com/watch?v=q19fw24pvn8

#### Can You Apply It?

1. Explain in general terms how a remote control works.
2. What property of light waves explains why a remote control doesn’t work if someone stands between the remote and the TV?
3. Explain why you can control a TV with a remote that is pointed at a mirror opposite the TV.
4. You can’t directly see the infrared light emitted by a remote control. How can you use a camera to see the infrared light?
5. How are signals encoded in the infrared light that is emitted by a remote control? What controls the signals?

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