Engineering Inside:

2016 Issue 1
Light

Remote Control Reflection

February 2016

by Robin Hegg

TV remote control in man's hand on a dark background with flare light

Infrared radiation is widely used in technology, ranging from night vision (in which infrared radiation is detected when there isn’t enough visible light to see an object) to studying the composition of materials through a process called spectroscopy. Infrared radiation is also used in the study of weather, the observation of space objects by astronomers, and in communications devices, including remote controls.

Infrared (IR) radiation is electromagnetic radiation with a wavelength longer than visible light but shorter than radio waves. Red is the color of visible light with the longest wavelength. “Infra” is Latin for “below,” so infrared is “below red.”

In remote controls, infrared light-emitting diodes (LEDs) emit infrared radiation, which is then focused by a plastic lens into a narrow beam. The infrared beam switches on and off to encode data. Since infrared radiation doesn’t go through walls, it won’t interfere with devices in other rooms.

In this activity, you will explore how the infrared radiation from a remote control interacts with different materials by trying to bounce the IR beam off of a material to control a television from around a corner.

Materials

A remote control

The television controlled by the remote control

White paper

Black paper

Aluminum foil: one flat sheet, one crumpled sheet

Plastic wrap

A CD

A glass of water

A glass of milk

Black electrical tape

Steps

1. For each of your materials (white paper, black paper, flat aluminum foil, crumpled aluminum foil, plastic wrap, a CD, a glass of water, a glass of milk, and black electrical tape) predict what will happen if you try to bounce your remote control’s infrared radiation beam off of it.

2. Next, test your predictions by trying to bounce the remote control’s infrared beam off of each material to see if it still controls the television.

3. Try the same experiment, but with the lights off.

4. Based on your results, develop a plan to turn on the television from another room or from around a corner. Decide what materials you will need and plan what you will need to do.

5. Test your plan.

Questions

1. How did your predictions about the different materials compare to the results of your research?

2. What materials were able to reflect the remote control’s infrared radiation beam? What materials weren’t? Do the materials that successfully reflected the remote control beam have properties in common? Why do you think those materials worked the others didn’t?

3. What do you think happened to the remote control beam when it reached the materials that didn’t reflect it?

4. How did your results differ in the dark? Why do you think that is?

5. Was your plan to turn on the television from another room or around a corner successful? If not, what do you think the problem was? What could you change about your plan to make it work?

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