Download The Electromagnetic Spectrum

Name _________________________________________________ Period ______ Date __________________
The Electromagnetic Spectrum
What is an electromagnetic wave?
Light is an electromagnetic wave. Light is a wave, like sound and the ripples on a pond. What
is oscillating in a light wave? Imagine you have two magnets. One hangs from a string and the
other is in your hand. If you wave the magnet in your hand back and forth, you can make the
magnet on the string sway back and forth. How does the oscillation of one magnet get to the
other one? Magnets create an invisible magnetic field around them. When you move a
magnet up and down, you make a wave in the magnetic field. The wave in the magnetic field
makes the other magnet move.
Oscillations of electricity or magnetism create electromagnetic waves
Anything that creates an oscillation of electricity or magnetism also creates
CHAPTERelectromagnetic
24: THE PHYSICAL NATURE OF LI
waves. If you switch electricity on and off repeatedly in a wire, the oscillating electricity makes
an electromagnetic wave. This is exactly how radio towers make radio waves. Electric
The electromagnetic
spectrum
currents oscillate up and
down the metal towers and create electromagnetic waves of theHow
right does an
frequency
to
carry
radio
signals.
Tapping
a
stick
up
and
down
in
a
puddle
makes
ripples
that
electromagnetic
wa
Properties of Like all waves, electromagnetic waves (like light) have frequency,
spread out wavelength,
from where amplitude,
you tap. Oscillating
electric
current
in
a
radio
tower
makes
ripples
of
electromagnetic
and speed. Also like other waves, electromagnetic
Electromagnetic wave
electricity
spread out
fromfrequency.
the tower
at the
speedoneof light as
waves and
wavesmagnetism
carry energythat
in proportion
to their
Shaking
a magnet
magnetic and electrica
electromagnetic
waves.
million
times per second (1 MHz) takes more energy than shaking it once per
The two qualities exch
back and forth like a p
second (1 Hz). That is why a 1 MHz electromagnetic wave has a million times
Properties of electromagnetic waves
exchanges potential a
more energy than a 1 Hz electromagnetic wave of the same amplitude.
Like all waves, electromagnetic waves (like light) have frequency, wavelength, amplitude, and
energy back and forth
Why visible
light
all electromagnetic
waves are invisible
for carry
the same
reasoninyou
cannot
speed.
AlsoAlmost
like other
waves, electromagnetic
waves
energy
proportion
to their
chapter 17 you learne
isfrequency.
different Shaking
see the magnetic
field
between
magnets.
The exception
visible
light.energy than
a magnet
one
milliontwo
times
per second
(1 MHz)istakes
more
induction; a changing
Visible
includes
only the
electromagnetic
waves
with the range of
energy
shaking it once
perlight
second
(1 Hz).
That
is why a 1 MHz
electromagnetic
wave
has a million
field induces an electr
can be
detected
the human eye. wave of the same amplitude.
times more that
energy
than
a 1 Hzbyelectromagnetic
vice versa. Induction i
.
The The entire range of electromagnetic waves, including all possible frequencies,
electromagnetic wave
Why visibleislight
is the
different
electromagnetic
called
electromagnetic spectrum. The electromagnetic spectrum
and spread. Each cyc
Almost all electromagnetic waves are invisible for the same reason you cannot see the
spectrum
includes radio waves, microwaves, infrared light, ultraviolet light, X rays, and
electric part of the wa
magnetic field between two magnets. The exception is visible light. Visible light includes only
magnetic wave as it c
gamma rays. Visible light is a small part of the spectrum in between infrared
the electromagnetic waves with the range of energy that can be detected by the human eye.
Each cycle of the mag
and ultraviolet light.
in turn creates a new
electric wave. The ele
magnetic parts of the
regenerating each oth
wave propagates.
UNIT 8 LIGHT AND OPTICS
Name _________________________________________________ Period ______ Date __________________
The electromagnetic spectrum
The entire range of electromagnetic waves, including all possible frequencies, is called the
electromagnetic spectrum. The electromagnetic spectrum includes radio waves, microwaves,
infrared light, ultraviolet light, X rays, and gamma rays. Visible light is a small part of the
spectrum in between infrared and ultraviolet light.
Like other forms of high-energy electromagnetic waves, ultraviolet light has enough energy to
remove electrons and break chemical bonds. Sunlight contains ultraviolet waves. A small
amount of ultraviolet radiation is beneficial to humans, but larger amounts cause sunburn, skin
cancer, and cataracts. Most ultraviolet light is blocked by ozone in Earth’s upper atmosphere.
Radio waves are the lowest-frequency waves. They have wavelengths that range from
kilometers down to tens of centimeters (Figure 24.4). Radio broadcast towers are tall because
they need to be one-quarter of a wavelength high to efficiently create the large wavelengths of
radio waves.
The speed of light
All electromagnetic waves travel at the same speed in a vacuum, the speed of light — 3 × 108
m/sec. As with other waves, the speed of light is the frequency multiplied by the wavelength.
Questions
1. Describe an electromagnetic wave. How is one made?
2. What is the relationship between the frequency of light and its wavelength?
3. What is the speed of light? ________________.
4. Compare and contrast a radio wave and ultraviolet light.
5. Radio waves, X rays, gamma rays, and visible light are all part of the ________________.
6. ________________ is the type of electromagnetic wave that can cause sunburn.
7. ________________ are produced by oscillations of electricity or magnetism.
8. ________________ is the type of electromagnetic wave we feel as heat.
9. The part of the electromagnetic spectrum we can see with our eyes is called
________________.
10. ________________ are the highest frequency waves in the electromagnetic spectrum
and are generated in nuclear reactions.