Transcript Chapter 11 PPT

Electromagnetic Waves
Chapter 11
Section 1
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What are Electromagnetic Waves?
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Vocabulary: electromagnetic wave; photon
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How does a vibrating electric charge produce an
electromagnetic wave?
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What properties describe electromagnetic waves?
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How do electromagnetic waves transfer energy?
What are Electromagnetic
Waves?
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Waves are produced by something that vibrates and
carry energy from one place to another
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We learned that waves such as sound cannot move
unless they have matter (or a medium) to transfer the
energy through
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BUT there is one type of energy that does not require
matter


The electromagnetic wave is made by vibrating electric
charges.
They are composed of changing electric fields and
magnetic fields
Properties
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The vibrating electric and magnetic fields of an
electromagnetic wave are perpendicular to each other
(pg340). This is also a transverse wave.
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In a vacuum, all electromagnetic waves travel at
300,000 km/s. Light is a type of electromagnetic
wave which is why its called the “speed of light”.
Nothing travels faster than the speed of light.

Wavelength is the distance from crest to crest and
frequency (hertz) is the number of wavelengths that
pass a point in a second. As frequency (f) increases,
the wavelength (λ) becomes smaller.
Matter &
Electromagnetic Waves
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Electromagnetic waves can make objects hot such as
asphalt
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This energy is called radiant energy
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Radiant energy makes fires feel warm and enables
you to see
Waves & Particles
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A wave is a disturbance that carries energy; particle
is a piece of matter

Albert Einstein provided an explanation to Heinrich
Hertz’s experiment of creating a spark by shining
light on a metal. Einstein said an electromagnetic
wave can behave as a particle called a photon. A
photon is a massless bundle of energy that behaves
like a particle. As the frequency increases, the energy
of the photon increases.
Section 2
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The Electromagnetic Spectrum
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Vocabulary: radio waves, microwaves, infrared waves,
visible light, ultraviolet waves, X-rays, gamma rays
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What are the main divisions of the electromagnetic
spectrum?
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What are the properties of each type of electromagnetic
wave?
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What are some common uses of each type of
electromagnetic wave?
A Range of Frequencies
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Wide range from vibrating once each second or
trillions of times each second
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The entire range of frequencies is called the
electromagnetic spectrum

Each section has a specific name (pg 345)
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Each region interacts with matter differently and the
human eye only detects a small portion called visible
light.
Radio Waves
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Longer than 10 cm
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Long wavelengths and low frequencies
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You hear sound when your radio changes the radio
wave into a sound wave
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Radar: Radio Detecting And Ranging; used for
tracking
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MRI create a map of different tissues to provide an
inside picture of the patient’s body which is
produced painlessly
Microwaves
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Wavelengths between 0.1 mm and 30cm but 1cm to
20 cm are used in communication such as cell
phones and satellites. Most familiar with microwave
ovens.

Microwave ovens interact with water, which is why
you have a defrost setting on the microwave because
the water molecules in crystallize form cannot rotate.
Infrared Rays
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You feel warmth from these wavelengths that range
from about a thousandth of a meter to a about 700billionths of a meter
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Hotter objects emit more infrared waves than cooler
objects
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Used by firefighters, energy-efficiency of a structure,
CD-ROM drives, TV remote controls
Visible Light
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Range you can detect with your eyes with wavelengths
around 700-billionths to 400-billionths of a meter
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Visible light only differs from radio waves, microwaves,
and infrared waves by its frequency and wavelength
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Color is the brains interpretation of the light absorbed
by substances in the eye
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Short wavelengths are violet to long such as red
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If all colors are present in the same place, you see white
Ultraviolet Waves
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UV waves can enter cells making them both harmful
and useful
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Can cause sunburn (UVA & UVB) but some
exposure is healthy because it creates vitamin D.
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It can disinfect food, water, medical supplies
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Fluoresce power to reveal fingerprints
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Ozone layer
X-Rays
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Penetrate skin and soft tissues but not denser
material such as teeth and bones (Low doses)
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Used in airport screening
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Can be harmful and both helpful to humans
Gamma Rays
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High frequencies and highest-energy photons
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Can penetrate several centimeters of lead
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Produced by processes that occur in the nuclei of
atoms
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Can be focused to an area and cause cancer cells to
die which unfortunately also kills healthy cells in the
process
Section 3
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Radio Comunication
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Vocabulary: carrier wave, modulation, analog signal,
digital signal, transceiver, Global Positioning System
(GPS)
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How are carrier waves modulated to transmit
information?
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What is the difference between amplitude
modulation and frequency modulation?
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What technologies use radio waves and microwaves
for communication?
Radio Transmissions
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Each radio, cell and television station uses an
assigned frequency so stations don’t interfere with
each other (pg 352)- AM, FM, etc.
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Specific frequency to which a station is assigned is
called the carrier wave
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Know the difference between FM and AM radios
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Closer to the tower the stronger the signal; bad
weather, surrounding mountains and artificial
structures can interfere with radio transmissions
The Digital Revolution
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Analog signals are electric signals whose values
change smoothly over time
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Digital signals, started in 2009, is an electrical signal
where there are only two possible values, on and off.
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Converter boxes
Telephones
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Used to be connected with wires
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Cell phones are transceivers which transmits one
radio signal and receives another radio signal
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Pagers work in a similar fashion
Communications Satellites
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Microwave signal is sent to the satellites and as a
transceiver it sends pack to a particular region on
Earth
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Satellite cell phones such as when crossing the ocean
there are no towers to switch between; delay in twoway communications
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Dishes uses microwaves rather than radio waves
GPS
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System of satellites, ground monitoring stations and
receivers that determine your exact location at or
above Earth’s surface
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Need four satellites to determine the location of an
object using a GPS receiver
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Owned and operated by USDoD but the signals sent
out can be used by anyone. Pet collars, airplanes,
ships, cars, etc.