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This is a lazer penBut, is it really a lazer? if it is what type of range would it have, and wheather it is or not, are they dangerous?
About range, in about 200 metres the beam has diverged from a few millimetres to 20-40 centmetres, so its intensity is very reduced; I think you won't be able to see it after 1 km even in complete darkness.
What makes a laser a laser is that it produces light by stimulated emision.
Surely most light is produced by spontaneous radiation?
The most expensive, ultra-short pulse lasers are the least monochromatic, but they are still useful
I meant that in all other sources most light is from spontaneous radiation so, overall, in the grand scheme of things, most light is spontaneous rather than, as you wrote "Light is produced by stimulated emission all around us, all of the time" I agree that some is, but it's very much the minority.
Also, I'm quite sure that more light spontaneously leaves the sides of a HeNe laser than comes out as the beam so, even in a laser, most of the light is spontaneous.
The requirement for short pulses for fast kinetics experiments also produces broad bandwidths so it's not just a matter of power. The high power ones are just the most fun :-)
Quote from: lightarrow on 10/05/2007 12:03:52About range, in about 200 metres the beam has diverged from a few millimetres to 20-40 centmetres, so its intensity is very reduced; I think you won't be able to see it after 1 km even in complete darkness.I am surprised at such a wide divergence from a laser beam - is this a deliberate safety measure, or just a limitation of the small size of the diode?