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The Electromagnetic Spectrum

 The electromagnetic spectrum is the complete
spectrum (or continuum) of all forms of “light”
 An electromagnetic wave consists of electric and
magnetic fields which vibrate - thus making waves.
 Vibrations
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 The electromagnetic spectrum consists of:
 radio waves
 cell phone waves
 microwaves
 radar waves
 infrared waves
 visible light waves
 ultraviolet waves
 x-ray waves
 gamma waves
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 Properties of electromagnetic waves include speed,
frequency and wavelength
 Speed (s), frequency (f) and wavelength () are related
in the formula:
 s = f x 
 All light waves travel at a speed of 3 x 108
m/s in a
vacuum
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 Frequency is the number of occurrence of a repeating
event per unit of time.
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 Wavelength is the distance between identical points.
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 Speed is the measure of how quickly distance changes
with time.
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All parts of the electromagnetic spectrum
travel at the same speed
Therefore, wavelength and frequency have an
indirect relationship.
This means that as one characteristic increases,
the other decreases
In other words, as wavelength increases,
frequency decreases
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Electromagnetic wave characteristics:
• short wavelengths have a high frequency
• long wavelengths have a low frequency
Electromagnetic waves & Energy:
• high frequency waves have high energy
• low frequency waves have low energy
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Fill in the table below:
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wavelength frequency energy
long
high

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increasing frequency increasing energy
If you haven’t already, sketch this drawing into your
notes. Don’t worry so much about the actual
wavelengths, just get the general shape and where the
various forms of light (radio, infrared, x-ray, etc) exist.
smaller wavelengths

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 Low energy waves with longest wavelengths
 Includes FM, AM, radar and TV waves
 Wavelengths of 1 m (10 -1
m) and longer
 Low frequency
 Used in many devices such as remote control items,
cell phones, wireless devices, etc.
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 Only radio waves are longer
 Wavelength 1 x 10-1
m to 1 x
10 - 4
m (1 m to 0.001 m)
 used for communication,
medicine and consumer use
(microwave ovens)
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 Invisible electromagnetic waves
that are detected as heat
 Can be detected with special
devices such as night goggles
 Used in heat lamps
 Higher energy than microwaves but
lower than visible light

 The portion of the electromagnetic spectrum that
human eyes can detect
 ROY G BIV (red, orange, yellow, green, blue, indigo,
violet)
 Which color has the lowest frequency?
 red has the lowest frequency – violet the highest
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Higher energy than light waves
Can cause skin cancer and blindness in humans
Used in tanning beds and sterilizing equipment
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 High energy waves
 Used in medicine, industry
and astronomy
 Can cause cancer
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 Highest energy
 Blocked from Earth’s
surface by atmosphere
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① What is the relationship between
frequency and wavelength?
① What characteristic of gamma waves
gives them their high energy?
① What does ROY G BIV mean? What
part of the electromagnetic spectrum
does it refer to?
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④ Which color is more energetic, red or
yellow?
⑤ Which type of wave travels faster,
gamma or radio?
⑥ Why are microwaves more dangerous
than radio waves?
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⑦ You have just been involved
in a traffic incident that leaves
you stranded on the side of
the road. Which part of the
electromagnetic spectrum
would be of the most use to
you and why?
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① Frequency and wavelength are properties of waves and since speed is constant for
em waves, as frequency increases, wavelength decreases. In other words, they
have an indirect relationship.
① Gamma waves get their high energy from their extremely short wavelengths (or
extremely fast frequency)
① ROY G BIV stands for “red, orange, yellow, green, blue, indigo, and violet. They
are the colors of the visible light in order of longest wavelength to shortest
wavelength.
① Yellow is more energetic than red because it has a shorter wavelength (or larger
frequency)
① Gamma waves and radio waves travel at the same speed
① Microwaves are more dangerous than radio waves because they have a higher
frequency and carry more energy.
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