electromagnetic spectrum.ppt

7/27/2019 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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electromagnetic spectrum.ppt

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