Download - electromagnetic spectrum.ppt
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Electromagnetic Waves &
the Electromagnetic Spectrum
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Electromagnetic Waves Transverse waves without a medium! (They can travel through empty space)
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They travel as vibrations inelectrical and magnetic fields.
Have some magnetic and someelectrical properties to them.
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When an electric field changes, so does themagnetic field. The changing magnetic field
causes the electric field to change. When onefield vibratesso does the other.
RESULT-An electromagnetic wave.
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Electromagnetic waves travel VERYFAST around 300,000
kilometres per second (the speedof light).
At this speed theycan go around theworld 8 times in onesecond.
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Waves or Particles?
Electromagnetic radiation has properties of
waves but also can be thought of as a streamof particles.
Example: Light Light as a wave: Light behaves as a transverse
wave which we can filter using polarized lenses.
Light as particles (photons): When directed at asubstance light can knock electrons off of asubstance (Photoelectric effect)
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Electromagnetic Spectrumname for therange of electromagnetic waves when
placed in order of increasing frequency
RADIO
WAVES
MICROWAVES
INFRARED
RAYS
VISIBLE LIGHT
ULTRAVIOLET
RAYS
X-RAYS
GAMMA
RAYS
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Notice the wavelength islong (Radio waves) and gets shorter (Gamma Rays)
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RADIO WAVES
Have the longest
wavelengths andlowestfrequencies of
all theelectromagneticwaves.
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Global Positioning Systems (GPS) measure thetime it takes a radio wave to travel from
several satellites to the receiver, determiningthe distance to each satellite.
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A radio picks up radio waves through anantenna and converts it to sound waves.
Each radio station in an area broadcasts at adifferent frequency. # on radio dial tells frequency.
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MRI(MAGNETIC RESONACE IMAGING)
Uses Short wave radio waves with amagnet to create an image.
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MICROWAVES
Have theshortest
wavelengths andthe highest
frequency ofthe radiowaves.
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Used in microwave
ovens. Waves transfer
energy to the
water in the foodcausing them tovibrate which inturn transfers
energy in theform of heat tothe food.
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RADAR (RadioDetection and
Ranging) Used to find thespeed of an objectby sending out radio
waves and measuringthe time it takesthem to return.
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INFRARED RAYS
Infrared= belowred
Shorterwavelength andhigher
frequency thanmicrowaves.
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You can feel thelongest ones as
warmth on yourskin
Warm objects
give off moreheat energy thancool objects.
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Thermograma picture that shows regions of differenttemperatures in the body. Temperatures are calculated by
the amount of infrared radiation given off.
Therefore people giveoff infrared rays.
Heat lamps give offinfrared waves.
http://www.snellinfrared.com/library/_view_msg.asp?refid=19 -
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VISIBLE LIGHT
Shorter wavelength andhigher frequency thaninfrared rays.
Electromagnetic waves wecan see.
Longest wavelength= redlight
Shortest wavelength=violet (purple) light
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When light entersa new medium it
bends (refracts).Each wavelength
bends a differentamount allowingwhite light to
separate into its
various colorsROYGBIV.
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ULTRAVIOLET RAYS
Shorterwavelength and
higherfrequency than
visible light
Carry moreenergy thanvisible light
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Used to killbacteria.
(Sterilizationof equipment)
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Too much can cause skin cancer.
Use sun block to protect against(UV rays)
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Causes yourskin to
producevitamin D(good for
teeth andbones)
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X- RAYSShorter
wavelength andhigher
frequency than
UV-raysCarry a great
amount of
energyCan penetrate
most matter.
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Bones and teethabsorb x-rays. (The light partof an x-ray image indicates a place where the x-
ray was absorbed)
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Too much exposurecan cause cancer
(lead vest atdentist protects
organs fromunnecessaryexposure)
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Used by engineersto check for tiny
cracks instructures.
The rays passthrough the
cracks and thecracks appeardark on film.
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GAMMA RAYS
Shorter wavelengthand higher frequency
than X-raysCarry the greatestamount of energy
and penetrate themost.
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Used in radiation treatment to kill
cancer cells.Can be very harmful if not used
correctly.
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The IncredibleHulk was the
victim ofgamma
radiation.
http://www.qksrv.net/click-291217-10273794?url=http%3A%2F%2Fwww.posternow.de%2Fonlineshop%2FDirectLinks.tpl%3Flan%3D1%26cod%3D1%26aid%3D8460 -
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Exploding
nuclearweapons emitgamma rays.
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Brief SUMMARYA. All electromagnetic waves travel at the samespeed. (300,000,000 meters/second) in avacuum.
B. They all have different wavelengths anddifferent frequencies. Long wavelength-lowest frequency Short wavelength highest frequency The higher the frequency the higher theenergy.
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