The Electromagnetic
Spectrum
Wavelength/frequency/energy
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Teacher Page
• Content: Physical Science—The
Electromagnetic Spectrum
• Grade Level: High School
• Creator: Dorothy Walk
• Curriculum Objectives: SC 1; Intro
Phys/Chem IV.A (waves)
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What is it?
• The electromagnetic spectrum is the complete
spectrum or continuum of light including radio
waves, infrared, visible light, ultraviolet light, Xrays and gamma rays
• An electromagnetic wave consists of electric and
magnetic fields which vibrates thus making
waves.
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Waves
• Properties of waves include speed, frequency
and wavelength
• Speed (s), frequency (f) and wavelength (l) are
related in the formula l x f = s
• All light travels at a speed of 3 s 108 m/s in a
vacuum
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Wavelength, Frequency and
Energy
• Since all light travels at the same speed,
wavelength and frequency have an
indirect relationship.
• Light with a short wavelength will have a
high frequency and light with a long
wavelength will have a low frequency.
• Light with short wavelengths has high
energy and long wavelength has low
energy
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Radio waves
•
•
•
•
•
Low energy waves with long wavelengths
Includes FM, AM, radar and TV waves
Wavelengths of 10-1m and longer
Low frequency
Used in many devices such as remote control
items, cell phones, wireless devices, etc.
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Microwaves
• Longer than radio, shorter
than light and infrared
• Wavelength 1 x 10 - 4 m to
1 x 10-1 m
• First used in radar, now
used in communication,
medicine and consumer
use (microwave ovens)
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Infrared waves
• 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
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Visible Light
• The portion of the electromagnetic spectrum
that human eyes can detect
• ROY G BIV (red, orange, yellow, green, blue,
indigo, violet)
• Red is the lowest frequency and violet is the
highest frequency
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Ultraviolet waves
• Higher energy than light waves
• Can cause skin cancer and blindness in
humans
• Used in tanning beds and sterilizing
equipment
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X-Rays
• High energy waves
• First discovered by
Roentgen
• Used in medicine,
industry and astronomy
• Can cause cancer
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Gamma rays
• Highest energy
• Blocked from Earth’s surface
by atmosphere
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Time to think…..
•
1. What is the relationship
between frequency and
wavelength?
•
2. What is meant by ‘spectrum’?
•
3. What does ROY G BIV mean?
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Now, let’s really think
• 4. Can you actually see x-rays?
– Support your answer.
• 5. Which color is more energetic, red
or yellow?
• 6. Which type of wave travels faster,
gamma or radio?
• 7. Why are microwaves more
dangerous than radio waves?
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Think about it….
• 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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Answers
• 1. Frequency and wavelength are properties of waves and since
speed is constant for em waves, as frequency increases,
wavelength decreases.
• 2. Spectrum is a continuum of all electromagnetic waves
• 3, ROY G BIV is the difference colors of the visible light in order of
longest wavelength to shortest wavelength.
• 4. X-rays can not be seen, only the waves in the visible light portion
are visible.
• 5. Yellow is higher energy than red because it has a shorter
wavelength and higher frequency.
• 6. Both travel at the same speed, 300,000 km/s (all em waves travel
at the same speed)
• 7. Microwaves have a higher frequency than radio and carry more
energy.
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