11.3
The Laser—A Special Type of Light
In the previous section, you learned about light from many different
sources. Each of those light sources emits electromagnetic radiation of many
different energies and in all directions. In this section, you will examine
lasers as a light source. You will also find out how laser light is different from
other forms of light.
Light from a laser has very special properties. Incandescent bulbs emit
electromagnetic waves of many different energy levels. A laser, in contrast,
produces electromagnetic waves of exactly the same energy level. This
results in visible laser light being of a very pure colour. If you shine red laser
light at a triangular prism, the light exiting the triangular prism will still
look red. Recall that white light shone at a triangular prism separates into
the colours of the visible spectrum.
Laser light is also very intense. This is because the electromagnetic waves
travel in exactly the same direction and the waves are exactly in unison
(Figure 1). These characteristics are very different from light radiating from
an incandescent bulb. That is why laser light is pure in colour, very intense,
and concentrated in one narrow beam. For this reason, you should never
look directly into a laser beam—it could damage your eyes. These unique
properties of lasers make them very useful. A high-energy laser can be used
to burn a hole through steel in a manufacturing process. It can also be used
by a surveyor to measure distances. Scientists have even
used lasers directed at the Moon to measure the
Earth–Moon distance 385 000 km
with an accuracy of 3 cm.
DID YOU KNOW?
Laser Tongue-Twister
“Laser” is an acronym for Light
Amplification by Stimulated Emission
of Radiation.
light bulb
(a)
(b)
NEL
light bulb
laser source
laser source
Figure 1 (a) The light bulb emits many
different electromagnetic waves.
(b) A laser emits electromagnetic waves
that are all exactly the same.
11.3 The Laser—A Special Type of Light
477
RESEARCH THIS
LASERS FOR DIFFEREnT USES
SKILLS: Researching, Communicating
There are many different kinds of lasers, and each kind has a
specific use (Figure 2). In this activity, you will research some
of these lasers and uses.
SKILLS HANDBOOK
4.A.
1. Research the characteristics and applications of helium-neon
lasers.
2. Research at least three practical applications of lasers. Find
out what type of laser is used in each case. Identify which
type of electromagnetic wave each laser produces.
3. Research the type of laser used to correct vision problems.
Identify which type of electromagnetic wave this laser
produces.
GO TO NELSON SCIENCE
A. What type of electromagnetic wave is produced by a
helium-neon laser? K/U T/I
B. What are three different types of lasers? Where is each of
these lasers used? K/U T/I
Figure 2 Lasers are often used in concerts or at dance halls.
In
C. Which laser is used to correct vision problems? What type
of electromagnetic wave does this laser produce? T/I
SUMMARY
• Laser light consists of electromagnetic waves of
exactly the same energy level, travelling in unison
in exactly the same direction.
CHECK
• Laser light is very pure in colour, is intense and
concentrated in one narrow beam, and can travel
great distances without spreading out.
YOUR LEARnIng
1. List three properties that make laser light different from
light emitted by an incandescent bulb or a flashlight. K/U
2. A laser with green light is shone at a triangular prism.
What will be the colour of the light leaving the prism?
Explain. K/U
4. Why should you never look directly into a laser beam? K/U
5. Use a diagram to illustrate how laser light is different from
white light. K/U
6. List at least four common applications of lasers that you
are familiar with. K/U
3. As you read in this section, scientists have used laser light
to accurately measure the distance between Earth and the
Moon.
(a) What properties of laser light allow us to measure
such great distances?
(b) Why could white light produced by a very powerful
searchlight not be used for this same measurement?
K/U
478
T/I
Chapter 11 • The Production and Reflection of Light
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