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)