Infra Red


How they're made

This radiant heater gives off lots of Infra red, as well as light

Infra red waves are just below visible red light in the electromagnetic spectrum ("Infra" means "below").

You probably think of Infra-red waves as heat, because they're given off by hot objects, and you can feel them as warmth on your skin.

Infra Red waves are also given off by stars, lamps, flames and anything else that's warm - including you.

The detector on this security light picks up the Infra red radiation from your body.


Infra-red waves are called "IR" for short.

They are used for many tasks, for example, remote controls for TVs and video recorders, and physiotherapists use heat lamps to help heal sports injuries. IR is also used for short-range communications, for example between mobile phones, or for the Dolby Screentalk headset system used in some cinemas.

Because every object gives off IR waves, we can use them to "see in the dark". Night sights for weapons sometimes use a sensitive IR detector. Remember the film, "Predator"?

Mobile phone cameras can 'see' infra red

It might surprise you to know that you probably have an Infra red-sensitve camera in your pocket right now.!

CCD chips are used as pickup devices in digital cameras, including camcorders and mobile phone cameras.

In fact, the CCD chip has a filter on it to stop most of the infra red from messing up the picture. But the photo shows that enough gets through to tell if a TV remote control is working or not. Try it - a handy diagnostic tool in your pocket!

This YouTube clip shows it nicely:

Want to make an infra red camera using an old webcam? There are instructions at

You'll also learn something interesting about £5 notes...

Apart from remote controls, one of the most common modern uses for IR is in the field of security.

"Passive Infra-Red" (PIR) detectors are used in burglar alarm systems, and to control the security lighting that many people have fitted outside their houses.

These detect the Infra-Red emitted by people and animals.

You've probably seen TV programmes in which police helicopters track criminals at night, using "thermal imaging" cameras which can see in the dark.

Infra-red satellite photo, showing weather patterns

These cameras use Infra-Red waves instead of "ordinary" light, which is why people look bright in these pictures. Similar cameras are also used by fire crews and other rescue workers, to find people trapped in rubble.

Weather forecasters use satellite pictures to see what's heading our way. Some of the images they use are taken using IR cameras, because they show cloud and rain patterns more clearly.


The danger to people from too much Infra-Red radiation is very simple - overheating.