8+
Gallery 7

Thermal Camera

A black thermal camera enclosed in a protective perspex box, pointing at two red upright display boards with people in the background
A monitor showing the room in a blue colour, with green, yellow and red shapes of people standing out.

Thermal cameras detect human body heat and some materials are transparent to the naked eye, but do not allow detection of body heat by the thermal camera.

How it works

Find a panel of material to hide behind to avoid being detected by the thermal camera. The video screens show what the thermal camera ‘sees’.

Things to try or ask around the exhibit

  • Which materials let visitors hide from the camera?
  • Which materials let visitors hide from human view?
  • What’s the difference between infrared used in a remote control and infrared emitted by warm bodies?
  • Do some parts of the human body emit more heat than others? How does the head compare to the hands?
  • Clap or rub your hands and check your palms on the screen—what does this show? The friction makes your hands warmer.
  • Touch each material panel with your hand. How does the stainless steel panel feel compared to the timber panel?

Background

The thermal camera detects IR (infrared) radiation that human eyes cannot detect. Some materials are ‘transparent’ to human vision, while other materials are transparent for the thermal camera. IR is a type of electromagnetic radiation that is not visible to human eyes, but humans can sense certain, longer IR wavelengths as heat or warmth being emitted from warm bodies. IR is emitted by all objects, more so at higher temperatures. Thermal cameras are used to detect collisions inside machinery and to check whether balls strike a bat during cricket matches. They also detect drafts in houses, human bodies in dark, smoky environments and even sick plane passengers who are developing a fever.

The material panels are roughly the same temperature. The steel should feel quite cool to the touch, but when seen through the camera, it appears to have the same temperature as the timber. This is because the steel is a better conductor of heat than the timber. The steel is not cold. Rather, it carries the heat of your warm hand away from you and through the metal. So, instead, your hand feels colder than it did before. The timber, by comparison, does not conduct heat as quickly as the metal, so that your hand keeps most of its heat and does not feel much colder than before you touched the timber

The thermal camera detects IR (infrared) radiation that your eyes cannot see, and the video screen shows what the thermal camera ‘sees’. The timber and polyethylene panels are opaque to visible light. You cannot see through them, but they let IR pass through, so the camera can ‘see’ through them. The glass panel is transparent and allows visible light to pass through. You can see through it, but it blocks IR, so the camera cannot ‘see’ through it. The stainless steel panel reflects IR like a mirror, so you can see IR-emitting bodies located nearby.

Visible light, as humans know it, is a very small part of the spectrum and is the only part that humans can see. The whole spectrum includes (in increasing energy) radio waves, microwaves, IR, visible light, UV (ultraviolet), X-rays and Gamma rays. Even within the IR part of the spectrum, there are different types or wavelengths of IR. ‘Near infrared’ is closest to the microwave end of the spectrum, and Near IR is used within remote controls around the house and can be detected by night vision goggles. The long wavelength IR is closer to the visible light end of the spectrum and is detected by thermal imaging cameras, such as those used in the exhibit.

Finding the science in your world

Thermal camera technology is used in factories to detect whether machines are malfunctioning, or video umpiring in international cricket, to detect whether the ball hit the bat.