f. Light travels in a wave that is up-and-down while still moving forward. Think
of a ball bouncing along a straight hallway. The ball bounces up and down while
moving down the hall. A wavelength for light is the distance between bounces.
Figure 2-11. A light wave.
g. A laser is, then, light energy stored under pressure. When the pressure is
great enough, that light energy is released in a huge, high-powered burst of light which
is the laser beam. Laser beams have a wide variety of uses.
a. Point of Sale Device. In the last 30 years, scientists have discovered more
and more uses for lasers. The general public is probably unaware that the point of sale
device in supermarkets functions by laser beam. The label, a series of parallel bars of
varying widths, is put on an item by the manufacturer. At the checkout counter, the
cashier moves that label across a focused laser beam. The laser beam scans the label,
detects variations in the light and dark bands, and converts the variations to electrical
signals. The price of the item is then identified and added to the customer's bill.
b. Videodisc System. The videodisc system, the space-age version of the
phonograph needle, is another increasingly popular laser-base device. The videodisc is
similar to a phonograph record. A major improvement is that the videodisc contains
information that can be converted to a standard video signal for playback on the home
television set. Information is put on the videodisc by laser beam, and the pictures on
the videodisc are played by a focused laser beam. There are many advantages in this
system. Since there is no needle to scratch or wear out the disc, there is no wear and
tear on the disc. Much more information can be stored on the videodisc because a
tightly focused laser beam is used in making the disc. It is easy to freeze a picture to
look at; just maintain the laser beam on the same track.
c. Military Application of Lasers.
(1) In the armed forces, there are two types of use for laser beams:
nondestructive use and destructive use. Nondestructive use includes a laser beam
being used as a guidance device for range finding, tracking flying aircraft, and in
battleground simulation on land. Destructively, it is possible to use high-powered laser
equipment to project lethal laser beams at a target, destroying the target swiftly and
instantly. That destruction can be accomplished by aiming a powerful pencil beam of
laser at the target's strategic points and deactivating the functioning system of the