What you need:
- a TV (or similar) remote control
- a smartphone camera
What to do
- Point the remote at yourself and look at it through a smartphone camera.
- Press and hold down any of the remote control’s buttons.
- You should now be able to see a flashing light signal at the tip of the remote on the phone screen (it is a purple glow in the photo above).
- You may have to use the reverse video chat camera if it doesn’t work on the main phone camera.
What’s happening?
We can’t detect infrared radiation with our eyes but we feel it as warmth when we stand under a heater bulb in the bathroom.
Infrared is a form of light, just like radio waves, microwaves and ultra-violet light. It has a longer wavelength than red light, and a shorter wavelength than radio and microwave.
Infrared radiation was detected by Sir William Herschel in 1800 when he was measuring the temperature in a spectrum that he made by passing sunlight through a prism. The thermometer was warmest when it moved to the side of the spectrum, past the visible red light.
Most ordinary digital cameras have an infrared filter that stops them seeing this long wavelength form of light, but many phone cameras don’t have this filter (though sometimes the main camera on a phone does have an IR filter).
