I’ve seen how you can test remotes by pointing them at your phone’s camera; when you press a button on the remote the phone screen shows a purplish light coming out of the remote that is invisible to the human eye. The signal coming from the remote is infrared though, making it closer to reds than to blues and purples, so why does it look purple on a phone screen?
In: Technology
The camera is picking up the harmonics of the light. It is much easier to think of it in terms of sound as this is how most people experience waves. Visible light fits pretty tightly in the space of a single octave. So if red is a C on a keyboard you would go up with orange being a D, yellow is E and so on to violet which would be a B. The next tone would be a C in a higher octave but our eyes is not able to see that far. Similarly the infrared spectrum would be notes that is lower then the C that is red but are again outside of our spectrum. However digital cameras have a strange quirk where they are able to detect infrared but will detect them as an octave higher. So infrared gets detected as blue light just as you detect a low C as the same note as a high C just higher.
Latest Answers