A Logitech Pro 4000 webcam was converted to an IR (infrared) camera by scratching off the reflective IR coating from a glass plate filter, allowing IR to enter, and introducing two sheets of exposed film (negative) in place of the coating to block visible light.
A TV controller typically uses infrared and can be seen as a bright light when pointed at this detector. This can be seen even when the IR filter is in place. The transmission is much better without it. The sensitivity to this “invisible light” may be demonstrated in class with a TV controller, as can utilizing the controller as a light to illuminate your face in a darkened room. Another thing that can be demonstrated is the appearance of money, like the $10 bill, that has missing bands of information in the infrared spectrum.
I’ve also removed the IR filter from an old digital camera. The camera produced the image to the left.