Not advanced science, just a little application made possible by technology. To check a remote control, you need a digital camera, a cellphone with camera will do. Turn the camera on, aim the remote at the lens of the camera, and press the button you want to test. If the button works, you see a flash on the display of the camera. The infrared light of remotes is invisible for the human eye, but the camera's image sensor picks it up, and shows it as white light on the display.
Many camera sensors are inherently IR sensitive, and so require an IR filter. Some photographers dabble in IR photography by removing the filter from an old camera. There are numerous examples all over the Web. Plants generally look white, thus making the scenes look like winter photos.
I had an 8mm camcorder (no longer works) that came with an IR remote. I composed a few "video letters" to a friend (this was the early 90s) and I used the remote to start and stop the camera as needed since I didn't have a "cameraman". I discovered what you did. The signal from the remote was converted to visible light by the camera. It looked like I repeatedly aimed an LED flashlight (years before they became popular) at the viewer of the tape. Sincerely, Bill
I used to do this all the time with my old Nokia, and even my G1, but my Galaxy Note has an IR filter and it just doesn't work. Which makes me want CCDs that are IR-RGB-UV sensitive so I can dial up the spectrum I want to photograph in.