chapter 17 the electromagnetic spectrum 17... · 2018. 8. 30. · electromagnetic spectrum? travel...
TRANSCRIPT
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Chapter 17 The Electromagnetic
SpectrumWhat is the
electromagnetic spectrum?
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The Nature of Electromagnetic Waves
Section 1
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Section 1 Vocabulary Electromagnetic wave
Electromagnetic radiation
Electromagnetic spectrum
Polarized light
Photoelectric effect
Photon
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What is an electromagnetic wave?
A transverse wave
Transfers electrical and magnetic energy
Consists of electric and magnetic fields moving through space at the speed of light
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Producing Electromagnetic Waves
Produced by charged particles
When moved, produces a magnetic field
When motion changes, magnetic field changes
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Energy - electromagnetic radiation
Speed - in a vacuum: about 300,000 kilometers per second
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Models of Electromagnetic Waves
Wave model
• Vibrates in one direction
• Called polarized light
Particle model
• Photoelectric effect / photon
• Albert Einstein
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Waves of the Electromagnetic Spectrum
Section 2
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Section 2 VocabularyRadio waves
Microwaves
Radar
Infrared rays
Thermogram
Visible light
Ultraviolet rays
X-rays
Gamma rays
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What is the Electromagnetic Spectrum?
Travel at same speed in a vacuum
Have different wavelengths
Different frequencies
Complete range of waves in order of increasing frequency
Includes radio waves, infrared rays, visible light, ultraviolet light, X-rays, and gamma rays
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Radio Waves
Longest wavelengths
Lowest frequencies
Include broadcast waves and microwaves
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Infrared Rays
Wavelengths shorter than radio waves
Heat lamps
Infrared cameras
• Thermograms
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Visible Light
Waves that you see
Colors of the visible spectrum: red, orange, yellow, green, blue, and violet
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Ultraviolet Rays
Wavelengths just shorter than visible light
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X-raysWavelengths shorter than ultraviolet rays
High frequencies
Carry more energy than ultraviolet rays
Can penetrate most matter
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Gamma RaysShortest wavelength
Highest frequencies
Radioactive substances
Nuclear reactions
Objects in space
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Producing Visible LightSection 3
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Section 3 VocabularyIlluminated
Luminous
Spectroscope
Incandescent light
Tungsten-halogen bulb
Fluorescent light
Vapor light
Neon light
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Object is illuminated if seen by reflected light
Object is luminous if it gives off light
Types of light bulbs: incandescent, tungsten-halogen, fluorescent, vapor, and neon lights
A Spectroscope views different colors of light produced by light bulbs
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Incandescent Lights
Glows
Filament inside gets white hot
Thomas Edison
Nitrogen and argon gases
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Tungsten-Halogen Bulbs
Tungsten filament
Halogen gas (iodine or bromine)
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Other Light SourcesFluorescent lights
• A gas
• Coated on the inside with a powder
Vapor lights
• Neon or argon gas
• Solid sodium or mercury
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Other Light SourcesNeon lights
• Sealed glass tube
• Neon gas
• Electric current passes through gas
• Electric discharge through gases
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Wireless CommunicationSection 4
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Section 4 Vocabulary
Amplitude modulation
Frequency modulation
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Radio and TelevisionTransmission antennas broadcast radio waves
Two methods of transmitting
• Amplitude modulation
• Frequency modulation
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Amplitude Modulation (AM)
Changes the amplitude of a wave
Long wavelengths
Easily reflected by Earth's ionosphere
Broadcast over long distances
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Frequency Modulation (FM)
Changes the frequency of a wave
Higher frequencies
More energy then AM waves
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The radio spectrum
• Federal Communications Commission (FCC)
• Very High Frequency (VHF)