See infrared light with a smartphone

Materials

For this activity, you will need:

• A television remote control or other infrared remote
• A smartphone, tablet or digital camera
• A darkened room
• A notepad and pen to record observations

How to see infrared light

Step 1: Set up your camera

1. Open the camera app on your smartphone, tablet or digital camera.
2. Point the camera at the front of a remote control.

Step 2: Observe the infrared signal

1. Press and hold one of the buttons on the remote control.
2. Watch the camera screen carefully.
3. Observe whether a flashing light appears at the end of the remote.
4. Record your observations.

Step 3: Compare what you see

1. Look directly at the remote while pressing the button.
2. Compare this with what is visible through the camera screen.
3. Record any differences you observe.

Step 4: Test different devices

1. Repeat the experiment using different remote controls, such as television, air conditioner or media player remotes.
2. If available, test different cameras, such as a smartphone, tablet or digital camera.
3. Compare the appearance of the infrared signals.
4. Record which devices detect the infrared light most clearly.

Step 5: Compare your results

1. Which remote produced the brightest signal?
2. Did all cameras detect the infrared light equally well?
3. Could you see the infrared signal without using a camera?

How does it work?

The remote control sends information using infrared light. Infrared is a type of electromagnetic radiation with wavelengths that are longer than visible red light.

When you press a button on the remote:

• The remote emits pulses of infrared light.
• These pulses carry information to a television, air conditioner or other device.
• Human eyes cannot detect infrared light.
• Some camera sensors can detect infrared radiation and display it on the screen as a flashing white, purple or pink light.

Although the remote appears inactive when viewed normally, the camera reveals the hidden infrared signal.

Infrared radiation is used in many technologies, including:

• Remote controls
• Thermal imaging cameras
• Night-vision equipment
• Scientific instruments
• Space telescopes

Science fair project: Take it further

Once you have observed infrared light from a remote control, investigate how different factors affect your results.

• Compare different types of remote controls. Do they all produce the same pattern of flashes?
• Test different cameras. Which devices detect infrared light most effectively?
• Observe the remote from different distances. How far away can the camera still detect the signal?
• Record a slow-motion video while pressing different buttons. Do different buttons produce different flashing patterns?
• Investigate whether the front-facing camera and rear-facing camera on a smartphone detect infrared light equally well.
• Research other parts of the electromagnetic spectrum, such as ultraviolet light, microwaves and radio waves. Which types of electromagnetic radiation can humans see, and which require special equipment to detect?
• Create a table to record your observations. Which camera detected the strongest signal? Which remote produced the brightest infrared light?