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#31
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Green vs. red laser toys
On Wed, 12 Aug 2009 23:50:36 +0100, Jack Campin - bogus address
wrote: I'm just back from Hungary and Rumania. I saw a shop in Budapest that specialized in selling illegal-in-the-UK combat knives to British tourists. One of the items they were selling was green lasers, so I assume those had to be powerful enough to be a weapon (and probably the same type the kids near Edinburgh Airport have). There have been occurrences reported to the UK CAA of pilots seeing lasers, which could be distracting. You also could cause the same trouble with a tightly focused spotlight. They don't put mandatory occurrence reports on line, at least not where I could find them, so actual details are lacking. This would affect aircraft taking off or landing, which would be the only times you could possibly shine a laser into the cockpit window from the ground. Someone came up with the name laser lout, which makes a good headline. Pocket lasers, including the green ones, sold to lecturers are 5 mW or less and are not dangerous. We use green laser pointers to point out stars to the public at astronomy club events and haven't put out an eye yet. We use green lasers because the red ones are hard to see. Bud |
#32
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Green vs. red laser toys
On Wed, 12 Aug 2009 19:01:52 -0500, William Hamblen wrote:
On Wed, 12 Aug 2009 23:50:36 +0100, Jack Campin - bogus address wrote: I'm just back from Hungary and Rumania. I saw a shop in Budapest that specialized in selling illegal-in-the-UK combat knives to British tourists. One of the items they were selling was green lasers, so I assume those had to be powerful enough to be a weapon (and probably the same type the kids near Edinburgh Airport have). There have been occurrences reported to the UK CAA of pilots seeing lasers, which could be distracting. You also could cause the same trouble with a tightly focused spotlight. They don't put mandatory occurrence reports on line, at least not where I could find them, so actual details are lacking. This would affect aircraft taking off or landing, which would be the only times you could possibly shine a laser into the cockpit window from the ground. Someone came up with the name laser lout, which makes a good headline. Pocket lasers, including the green ones, sold to lecturers are 5 mW or less and are not dangerous. We use green laser pointers to point out stars to the public at astronomy club events and haven't put out an eye yet. We use green lasers because the red ones are hard to see. Bud A handheld laser pointer is unlikely to cause permanent blindness at the distance from the ground to a landing or taking-off aircraft, but even dazzling the pilot's vision for thirty seconds or so could cause a crash under those circumstances. At indoor range, a handheld laser can indeed cause permanent vision damage if the beam happens to focus onto the point where the nerve bundle attaches to the retina. The problem is that, even though the total power of the beam is low, it focuses down onto a very small dot at the back of the eye, so the power level at that focal point can be high enough to cause permanent damage. -- John F. Eldredge -- "Reserve your right to think, for even to think wrongly is better than not to think at all." -- Hypatia of Alexandria |
#33
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Green vs. red laser toys
On 13 Aug 2009 03:07:11 GMT, John F. Eldredge wrote:
A handheld laser pointer is unlikely to cause permanent blindness at the distance from the ground to a landing or taking-off aircraft, but even dazzling the pilot's vision for thirty seconds or so could cause a crash under those circumstances. At indoor range, a handheld laser can indeed cause permanent vision damage if the beam happens to focus onto the point where the nerve bundle attaches to the retina. The problem is that, even though the total power of the beam is low, it focuses down onto a very small dot at the back of the eye, so the power level at that focal point can be high enough to cause permanent damage. You have a cite for a 5mw laser causing permenant eye damage? Try this test: go to the garage. Turn the car's headlights on. Shine a laser pointer on the wall where it is illuminated by the car's headlights. No dot? It is invisible because the car's headlights are so much more powerful. Of course, a laser doesn't disperse like a car's headlights. At 200' a laser pointer is going to be brighter than a car's headlights. But at anything less than about 20', a car's headlights are far brighter. |
#34
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Quote:
Update: apparently all of the answers to the universe's questions exist on YouTube. I just watched a video of a cat exposed to a dancing green laser dot and then a dancing red one. The cat didnt even seem to notice the green dot. But when the red one came on, it didn't take the kitty long to take notice. Here is the video, see for yourself: youtube.com/watch?v=Bj0C7mLG4DQ. Which means, the answer to the question appears to be that RED is the preferred color, all other things being equal. Last edited by KDS : March 7th 12 at 08:41 PM. Reason: New info |
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