I know this is way, way OT, but I also know that this ng has some of the most knowledgeable contributors.
Why, when a laser (say a CD player with the lid off) says it has an output wavelength of 850nm, can you see it as red? And, I have a fibre optic module that I'm playing with at work (again class
1), and you can see a red spot on this too (and it's also supposed to be 850nm).