CP Physics
Ms. Morrison
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Moving charged particles create magnetic
fields
Changing motion of charged particle creates
expanding and collapsing magnetic field which
generates and expanding and collapsing
electric field
Travel at 3.0 x 108 m/s through empty space ( c
= speed of light)
Travels more slowly through mediums
Energy depends on frequency
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Radio Waves
Microwaves
Infrared waves
Visible light
Ultraviolet light
X-rays
Gamma rays
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Lowest frequency
Longest wavelength
Least energy of spectrum
Carry sound waves
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Frequencies match natural frequencies of
molecules (fats, proteins, etc.)
Causes food molecules to vibrate making the
food cook itself
Icebergs give off microwaves
Match natural frequencies of some pacemakers
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Heat waves – all animals give off infrared
Uses:
Heat lamps
 Night vision
 Alcohol breath test
 Remote controls
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Only 1/1,000,000 of EM spectrum
Different frequencies seen as colors (ROY G
BIV)
Red light
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Lowest frequency (least energy)
Longest wavelength
Violet light
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Highest frequency (most energy)
Shortest wavelength
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Causes sunburns, damages tissues, and can kill
bacteria
UV-B rays more dangerous than UV-A because
they have higher frequency
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Produced by high speed electrons slamming
into a metal plate
Uses:
Medical X-rays (bones, teeth)
 Airport security
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Highest frequency of EM spectrum so highest
energy waves of spectrum and greatest
penetrating power
Shortest wavelengths of spectrum
Produced by nuclear particles and occur with
every nuclear reaction
Used in radiation therapy (kill healthy cells,
but kill cancer cells)
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Frequencies that eye is sensitive to
c = 3 x 108 m/s
c = λf
Transverse wave
Interaction with materials
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Transparent – all light transmitted, ex. Clear glass
Translucent – scatters light transmitted, ex. Frosted
glass
Opaque – does not transmit any light, ex. Brick
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Behaves like wave when traveling through
empty space or through a medium when it
does not interact with the medium’s particles
Behave like all other waves:
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Reflects
Refracts
Diffracts (ex. Prism – see colors of light)
Interferes
 Constructive – produces light bands
 Destructive – produces dark bands
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1900s – discovered that light can act like a
particle when it interacts with matter
Certain colors of light produce photosynthesis
when light absorbed by green leaves
Certain colors of light shown on metal plates
cause electrons to jump of the atoms and create
electric current (ex. Solar calculators)
Electrons jump to higher energy levels in atom
when absorb energy, when return to ground
level will emit specific color of light
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Explains how light interacts with matter
Photon = quantum of light energy (packet of
light energy)
Photon’s energy depends on its frequency – red
photons have less energy than violet photons
Dual Theory of Light: Light moves through
space as a wave and interacts with matter as a
particle
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Illuminated objects = reflect light, ex. Moon
Luminous objects = emit light, ex. Sun
Different methods to produce light based on
how they excite electrons:
Heating gases
 Heating metal filaments
 Electricity
 Ultraviolet radiation
 Chemoluminescence
 Bioluminescence
 Phosphorescence
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Only occurs with transverse waves
Polarized materials have molecules that only
allow EM waves of one direction pass through
them = polarizing axis
Blocks waves perpendicular to polarizing axis
Example, polarized sunglasses reduce glare of
light reflecting off a variety of surfaces