Which parts of your body are the hottest? You can’t see that with your naked eye, but you can with a thermal camera! This kind of camera visualises heat, or rather infrared radiation.
How? By capturing the radiation and converting it into an electrical signal. These signals are shown in a particular colour on the screen. If something is warm, you see it as a light colour (white-yellow). If something is cold, you see it as a dark colour (purple-black). Something in between? Then you see it as red.
Beside the screen you will also see some green metal figures. They are being kept cool. Put your hand on one of these shapes, and it will pass heat to the metal. In doing so, the skin on your hand becomes cold and you will see a cool tattoo appear on the screen!
What are those droplets on the green figures?
Not sweat from the person before you, just water. The warm air suddenly hits something very cold. Then the water vapour in the air turns to liquid due to the difference in temperature. Just like on the mirror when you have taken a hot bath or shower. We call this condensation.
Thermal cameras against virus transmission
During the corona pandemic, some hospitals installed a thermal camera at the entrance. With this, they could identify any patients or staff with a raised body temperature. This may indicate an infection with the virus. Anyone with a fever was immediately urged to contact the doctor.