Re: Powerful Green Laser Pointer - Visible 2 Miles Away

From: Chris L Peterson (clp_at_alumni.caltech.edu)
Date: 12/10/04 

Date: Fri, 10 Dec 2004 16:36:54 GMT

On Thu, 09 Dec 2004 19:59:00 GMT, "Big Cheese" <bigcheese@askmenoquestions.com>
wrote:

>I'm always concerned with accidentally hitting someone in the eye with one
>of these and, being so bright, possibly causing blindness or other damage.
>Or, inadvertently hitting a motorist passing by- could the temporary
>blindness cause an accident? Comments from the group? Am I just being an
>alarmist, or can these things happen and do they?

Hitting a driver in the eye and causing an accident is certainly a possibility,
although the contact time would be so brief that it shouldn't happen easily to
any competent driver- the effect is no worse than coming around a bend or out of
trees and finding the Sun suddenly in your eyes. Of course, many of the drivers
out there are far from competent! And used properly, by astronomers, there
should be very little chance of the beam intersecting a motorist.

As far as causing eye damage, there is really no possibility of this with
pointers that are 5mW or less (as all should be, legally). There isn't enough
energy in such a beam to cause damage within the natural reflexive aversion time
of the eye. Also, these lasers have quite large divergence. Once you are more
than a few meters away, 1/r^2 makes quick work of reducing the amount of energy
that reaches the retina.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

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