Okay, lots of info to go through.
Let's start with the little tangent about terminology:
Rockie wrote: ↑
Sun Jul 01, 2018 10:05 am
I thought I was pretty clear that people buy lasers because they're coherent...as in they do not diverge.
That suggests I know the difference between the two but I apologize if it was confusing.
Respectfully, the bold quote does indicate you do not know they are different. They are not the same. They are different properties of a laser.
Coherent means that the wavelengths of the light are in phase. This is important for data transmission applications and lots of experiments. For our "blind the pilot" task, this is irrelevant (unless you are trying to beam updated SOPs through his retinas
Divergence/divergent measures or refers to the widening of the beam. A laser has a very small non-zero divergence.
Granted, in our discussion it doesn't really matter which word you used, you and me are both referring to the diverging beam. I do admit I find it a bit funny that the wrong terminology is being used as a rebuttal to my suggestion to educate people more about lasers.
Rockie wrote: ↑
Sun Jul 01, 2018 10:05 am
Any laser I've seen diverges noticably within a large room. What kind of laser can you buy that doesn't diverge until 2000 feet, and why would Joe Laser guy buy one expecting it to be a death dot and then use it on an airplane?
Let's consider 2 lasers:
1) Laser A: a theoretically perfect laser. Does not diverge. All its power stays focused in the same narrow beam/dot, independent of distance
2) Laser B: a powerfull real laser. This laser does diverge and its power/beam spreads out like a cone.
Joe Laser wants to buy a laser to play around with. He doesn't know too much about it, but he is interested in it, and wants to shine on some objects. He buys laser B, but thinks he is buying laser A. Why? Because of movies, books, sci fi, flyers and promo material of the manufacturer. It's an expensive laser, so it must be close to perfect.
Joe is having fun shining at objects and he notices planes are flying over his house very often. He managed to shine on his neighbour's car, would he be able to hit the plane? He might even know he is not supposed to do that, but what are the chances of hitting the pilots in the eyes, right? They are all flying on auto pilot anyway and won't be looking outside. So he tries to hit the plane with his laser. I'm not sure what Joe would actually see, as I've never pointed a laser at an airplane.
If Joe was actually shining with laser A, there would be no effect to the plane. The chances of hitting one of the eyes of the pilots are practically zero. It's a bit like the warning "don't use your cellphone while fuelling": theoretically possible that it might cause a disaster, but realistically speaking, nothing will happen.
However, Joe is shining laser B. The beam diverges, the chances of hitting the cockpit of the plane increase and the pilots get blinded, possibly with permanent damage to the eyes.
Note, if laser A would hit a pilot, the damage would be worse than laser B, as laser A would send ALL the energy in the eye. At least with laser B only a fraction shines in the eye if you get hit.
Allow me to bring up an anology: I have a typical revolver with one bullet in it. I am willing to pay you 10k if I can shoot at your head. You can be in bulletproof armor, but no helmet.
I offer you the money to shoot you from 2 meter distance. Would you take the deal? Maybe you should, as I am a lousy shot, but you probably won't.
I offer you the money to shoot you from 7000 ft while you are flying a bullet proof airplane (open cockpit though) at 180 kts. Would you take the deal? You'd at least consider it. The chances of me hitting your head are practially zero. That is how it looks from Joe Laser's perspective as well: he incorrectly assumes he is trying to hit a plane with a revolver instead of with a machine gun.
Yes you say, but it diffuses over distance right and they know that which is why they shine it at airplanes but not their kids eyes. But digits_ is saying they don't know it diffuses. So they don't know it diffuses, and they don't know it's dangerous. ER's must be full of people with laser blindness.
Diffuse means that light gets scattered when it interacts with other particles. I don't believe I used "diffuse" anywhere in this thread.
They know it is dangerous to the eyes. They know it is easy to hit your eyes from short distance. They don't think they are able to hit the eyes of the pilots from 7000 ft, as they incorrectly assume the light does not diverge.
There's more than meets the eye when it comes to lasers.