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