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The Electromagnetic Spectrum The Nature of Electromagnetic Waves Waves of the Electromagnetic Spectrum Producing Visible Light Wireless Communication Table of Contents
The Electromagnetic Spectrum
The Nature of Electromagnetic Waves
Waves of the Electromagnetic Spectrum
Producing Visible Light
Wireless Communication
Table of Contents
The Electromagnetic Spectrum The Nature of Electromagnetic Waves
Electromagnetic WavesBelieve it or not, you are being “showered” all the time, not by rain but by waves.
The Electromagnetic Spectrum
Important Scientific DiscoveriesJames Clerk Maxwell first formally postulated electromagnetic waves. These were subsequently confirmed by Heinrich Hertz. Maxwell derived a wave form of the electric and magnetic equations, thus uncovering the wave-like nature of electric and magnetic fields, and their symmetry. Because the speed of EM waves predicted by the wave equation coincided with the measured speed of light, Maxwell concluded that light itself is an EM wave.According to Maxwell's equations, a time-varying electric field generates a time-varying magnetic field and vice versa. Therefore, as an oscillating electric field generates an oscillating magnetic field, the magnetic field in turn generates an oscillating electric field, and so on. These oscillating fields together form a propagating electromagnetic wave.
The Electromagnetic Spectrum
What are Electromagnetic Waves?
Electromagnetic waves are transverse waves that transfer both electrical and magnetic energy.
All electromagnetic waves consist of vibrating electric and magnetic fields that move through space at the speed of light (3.0 x 10^8 m/s)
The Electromagnetic Spectrum
Producing Electromagnetic WavesLight is an electromagnetic wave
All electromagnetic waves are produced by charged particles
Protons are positively charged (+)Electrons are negatively charged (-)
The electronic field produces electronic forces that push or pull on other charged particles.
The Electromagnetic Spectrum
Producing A Magnetic FieldA magnetic field is produced when a charged particle moves.The energy that is transferred through space by electromagnetic waves is called electromagnetic radiationElectromagnetic waves do not require a medium and therefore can travel through empty space (vacuum).
The Electromagnetic Spectrum The Nature of Electromagnetic Waves
What Is an Electromagnetic Wave?An electromagnetic wave consists of vibrating electric and magnetic fields that move through space at the speed of light.An electromagnetic wave is a transverse wave that transfers electrical and magnetic energy.
The Electromagnetic Spectrum The Nature of Electromagnetic Waves
Models of Electromagnetic WavesMany properties of electromagnetic waves can be explained by a wave model. Only some light waves pass through a polarizing filter. The light that passes through vibrates in only one direction and is called polarized light.
The Electromagnetic Spectrum
Electromagnetic Wave ModelsSometimes light behaves like a stream of particles of energy. When a beam of light shines on some substances, it causes tiny particles called electrons to move and produce an electric current. Sometimes a beam of light can even cause electrons to be knocked out of substances. This is called the photoelectric effect. It can be explained only by thinking of light as a stream of tiny packets of energy. Each packet of light energy is called a photon.
The Electromagnetic Spectrum
OutliningAn outline shows the relationship between main ideas and supporting ideas. As you read, make an outline about electromagnetic waves. Use the red headings for the main ideas and the blue headings for the supporting ideas.
The Nature of Electromagnetic Waves
The Nature of Electromagnetic WavesI. What Is an Electromagnetic Wave?
A. Producing Electromagnetic Waves
B. EnergyC. Speed
II. Models of Electromagnetic WavesA. Wave Model of LightB. Particle Model of Light
The Electromagnetic Spectrum
Electromagnetic Waves
Click the Video button to watch a movie about electromagnetic waves.
The Nature of Electromagnetic Waves
The Electromagnetic Spectrum
Links on the Nature of Waves
Click the SciLinks button for links on the nature of waves.
The Nature of Electromagnetic Waves
The Electromagnetic Spectrum
End of Section:The Nature of
Electromagnetic Waves
The Electromagnetic Spectrum Waves of the Electromagnetic Spectrum
What Is the Electromagnetic Spectrum?The electromagnetic spectrum is the complete range of electromagnetic waves placed in order of increasing frequency.
The Electromagnetic Spectrum
All electromagnetic waves travel at the same speed in a vacuum, but they have different wavelengths and different frequencies.
Recall: speed = wavelength x frequency
The Electromagnetic Spectrum
Scientific NotationFrequencies of waves often are written in scientific notation. A number in scientific notation consists of a number between 1 and 10 that is multiplied by a power of 10. To write 150,000 Hz in scientific notation, move the decimal point left to make a number between 1 and 10:
In this case, the number is 1.5. The power of 10 is the number of spaces you moved the decimal point. In this case, it moved 5 places:
150,000 Hz = 1.5 X 105 Hz
Waves of the Electromagnetic Spectrum
The Electromagnetic Spectrum
Scientific Notation
Practice Problem
A radio wave has a frequency of 5,000,000 Hz. Write this number in scientific notation.
5.0 X 106 Hz
Waves of the Electromagnetic Spectrum
The Electromagnetic Spectrum
Electromagnetic WavesElectromagnetic waves are all around you–in your home, your neighborhood, and your town.
Waves of the Electromagnetic Spectrum
The Electromagnetic Spectrum
Electromagnetic Waves Activity
Click the Active Art button to open a browser window and access Active Art about electromagnetic waves.
Waves of the Electromagnetic Spectrum
The Electromagnetic Spectrum
Previewing VisualsBefore you read, preview Figure 3. Then write two questions that you have about the diagram in a graphic organizer like the one below. As you read, answer your questions.
The Electromagnetic SpectrumQ. Which electromagnetic waves have the shortest wavelength?
A. Gamma rays have the shortest wavelength.
Q. Which electromagnetic waves have the lowest frequency?
A. Radio waves have the lowest frequency.
Waves of the Electromagnetic Spectrum
The Electromagnetic Spectrum
Electromagnetic Spectrum
Click the Video button to watch a movie aboutthe electromagnetic spectrum.
Waves of the Electromagnetic Spectrum
The Electromagnetic Spectrum
End of Section:Waves of the
Electromagnetic Spectrum
The Electromagnetic Spectrum ProducingVisible Light
Incandescent LightsAn incandescent light is a light bulb that glows when a filament inside it gets white hot.
The Electromagnetic Spectrum ProducingVisible Light
Neon LightsA neon light is a sealed glass tube that contains neon gas.
The Electromagnetic Spectrum
Feature
Comparing and ContrastingAs you read, compare and contrast the five types of light bulbs by completing a table like the one below.
Glass
Ordinary Light Bulb
Tungsten-Halogen Fluorescent Vapor Neon
Bulb Material
Hot/Cool
Makeup
Efficiency
Quartz Glass Glass
Hot Very Hot Cool
Tungsten filament and nitrogen gas and argon gas inside
Has tungsten filament and a halogen gas inside
A gas and a powder coating inside
Has neon or argon gas and solid sodium or mercury inside
Has neon gas inside
Not efficient More efficient than ordinary bulb
Very efficient Very efficient
ProducingVisible Light
Glass
Cool Cool
Very efficient
The Electromagnetic Spectrum
Data Sharing Lab
Click the PHSchool.com button for an activity about sharing data for the Consumer Lab Comparing Light Bulbs.
ProducingVisible Light
The Electromagnetic Spectrum
End of Section:Producing
Visible Light
The Electromagnetic Spectrum WirelessCommunication
Radio and TelevisionIn AM transmissions, the amplitude of a radio wave is changed. In FM transmissions, the frequency is changed.
The Electromagnetic Spectrum
Comparing Frequencies
The table shows the ranges of radio broadcast frequencies used for AM radio, UHF television, FM radio, and VHF television.
WirelessCommunication
The Electromagnetic Spectrum
Comparing Frequencies
Kilohertz (kHz) and megahertz (MHz)
Interpreting Data:
In the table, what units of measurement are used for frequency?
WirelessCommunication
The Electromagnetic Spectrum
Comparing Frequencies
UHF television uses the highest frequency radio waves, and AM radio broadcast uses the lowest frequency radio waves.
Interpreting Data:
Which type of broadcast shown in the table uses the highest frequency radio waves? Which uses the lowest frequency waves?
WirelessCommunication
The Electromagnetic Spectrum
Comparing Frequencies
UHF television uses waves with the highest frequency and therefore the shortest wavelength.
Calculating:
Which type of broadcast uses waves with the shortest wavelength?
WirelessCommunication
The Electromagnetic Spectrum
Comparing Frequencies
You cannot tell from this data if it is a television or radio program, because VHF television and FM radio both broadcast radio waves with a frequency of 100 MHz.
Inferring:
A broadcast uses a frequency of 100 MHz. Can you tell from this data if it is a television or radio program? Explain.
WirelessCommunication
The Electromagnetic Spectrum WirelessCommunication
Cellular Phone SystemIn the cellular phone system, cellular phones transmit and receive radio waves that travel to the nearest tower.
The Electromagnetic Spectrum WirelessCommunication
Communication SatellitesIn the Global Positioning System (GPS), signals from four satellites are used to pinpoint a location on Earth.
The Electromagnetic Spectrum
What You Know
What You Learned
Using Prior KnowledgeYour prior knowledge is what you know before you read about a topic. Before you read, write what you know about wireless communication in a graphic organizer like the one below. As you read, continue to write what you learn.
1. Cellular phones don’t use wires.2. Radio and television signals travel through the air.
1. The signals for radio and television programs are carried by radio waves.
2. The signals can be transmitted by changing either the amplitude or the frequency of the radio waves.
3. Cellular phones transmit and receive signals using microwaves.
WirelessCommunication
The Electromagnetic Spectrum
Links on Using Waves to Communicate
Click the SciLinks button for links onusing waves to communicate.
WirelessCommunication
The Electromagnetic Spectrum
End of Section:Wireless
Communication
The Electromagnetic Spectrum
Graphic Organizer
Magnetic fields
Electromagnetic waves
consist of travel at the speed of
have different
Electric fields Wavelengths
Light
Frequencies
The Electromagnetic Spectrum
End of Section:Graphic Organizer
