Lasers concentrate all their light in to a beam which can
be very narrow. There are regulations on the power levels for
lasers that are sold to the general public and they are
surprisingly low power such as ten milliwatts or so but the light
appears very bright due to the fact that all of it is
concentrated in a little spot maybe the size of the point of a
pin.
In addition, lasers are one frequency of light just like
a crystal-controlled transmitter transmits a carrier on only one
frequency which means that the light stays in a column over quite
a distance and does not spread out as much as light from a light
bulb or an LED which is several frequencies. If you could hear
the energy from a laser as sound, it would be a pure tone. An
incandescent light bulb or a LED would produce something that
sounded more like the hiss of noise. If you ran that through a
prism, you would see several slightly different shades of the
color of a LED and a fairly full spectrum from the incandescent
bulb. The laser would produce one sharp line of color if sent
through a prism or diffraction grating.
The green laser pointers that cause the biggest problem
with airplanes or people at a distance deliver even more energy
to the eye so they can temporarily blind someone easier than the
red laser pointers.
There are a lot of valid uses for those red and green
lasers but as long as we have idiots out there, some are going to
abuse them and cause trouble.
By the way, did you know that if you aim two lasers of
nearly the same frequency at a target, the two signals will
heterodyne just like two RF carriers. The reason is that they
really are two RF carriers that transmit at a frequency of radio
we call light.
The laser beam toys you describe do their thing by using
wiggling mirrors to reflect a beam left and right and up and down
in some sort of calculated way to produce projections.
If you had eyes capable of seeing really fast things like
bullets and the individual wing beats of flies and other bugs,
you would see a tiny spot of light racing back and forth and up
and down in a way that produces the picture you see. The human
eye has visual persistence which runs that rapid movement
together in to what looks for all the world like the shape of an
animal or person. It's pretty cool and rock bands that do laser
light shows have very expensive and complicated versions of those
same devices that can be programmed to produce anything your
imagination and the hardware will let you produce.
Martin
Phil Scovell <[log in to unmask]> writes:
> Although I was the first patient in the state of Iowa in October of 1964
> to
> have his retinas treated using a laser surgical machine, I never got to
> see
> an actual laser beam of light itself. By the way, the laser treatment did
> not work on me because my retinas were shredded, by this point, into tiny
> fragments and the lasers were not narrow beamed enough to tack anything
> down. I left totally blind on November 13 of 1964, and that was after 13
> operations and procedures before the laser came to the University of Iowa
> hospital. Anyhow, as my kids grew, laser beam toys became quite popular.
> As I recall, that last time my young son had one was when he was 14 or 15.
> It would display a picture of a bird on a wall from 40 feet away. Over
> the
> years, I've heard many reports, and just recently for that matter, of
> people
> lasering inbound commercial aircraft and blinding, to the point of
> distraction, the pilots. To accomplish this, there must be a long
> distance
> way of amplifying a laser beam to reach that far out to an approaching
> plane. I'm assuming, the more power, the longer the laser beam can reach
> but how much power would it take to reach hundreds of yards out to an
> approaching aircraft? I wouldn't think lasers of that type would be
> available on the open market but I haven't done that much reading about
> such
> a device in the first place. Anybody on here have some knowledge on the
> topic?
>
> Phil.
> K0NX
>
>
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