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17.2 NotesLight
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EM Waves have many uses
EM Waves have different frequencies
Electromagnetic Waves
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Range of all EM frequencies
Electromagnetic Spectrum
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Electromagnetic Spectrum
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Measured in Hertz – one cycle per second
Measuring EM Waves
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Radio Waves (Low Frequencies)MicrowavesVisible Light Infrared LightUltraviolet LightX-RaysGamma Rays (high frequencies)
Types of EM Waves
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Modulating Radio Waves
Modulation - variation of amplitude or frequency when waves are broadcast◦AM – amplitude modulation Carries audio for T.V. Broadcasts Longer wavelength so can bend around hills
◦FM – frequency modulation Carries video for T.V. Broadcasts
© 2000 Microsoft Clip Gallery
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◦Radio WavesDef. – Longest wavelength and lowest freq.
Uses – Radio, TV
Radio Waves
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Microwaves
***These were accidentally discovered for use to cook food
when microwaves melted a candy bar in a researcher’s pocket!
• Higher energy than radio waves• radar (detecting aircraft and ships) • cell phones (radio transmitter and receiver)
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Infrared Rays◦Infrared RaysDef – Light rays with longer wavelength than red light.
Uses: Cooking, Medicine, T.V. remote controls
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Infrared Light
Frequencies lower than visible light. They can not be seen but can be felt as heat..
We will see this in “The Core”
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Infrared Light
In other words, we experience this type of infrared radiation every day in the form of heat!
The heat that we feel from sunlight, a fire, a radiator or a
warm sidewalk is infrared. Infrared light is even used to heat food sometimes - special
lamps that emit thermal infrared waves are often used in fast food
restaurants!
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Infrared Light Examples
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Infrared Light Examples
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Old Faithful Yellowstone Park
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What is this?
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What do you see here?
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Ultraviolet Rays◦Ultraviolet rays.Def. – EM waves with frequencies slightly higher than visible light
Uses: food processing & hospitals to kill germs’ cells
Helps your body use vitamin D.
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X Rays
◦X-Rays Def. - EM waves that are shorter than UV rays.
Uses: Medicine – Bones absorb x-rays; soft tissue does not.
Lead absorbs X-rays.
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Gamma Rays
◦Gamma raysDef. Highest frequency EM waves; Shortest wavelength. They come from outer space.
Uses: cancer treatment.
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Clear Your Desks except for one piece of paper.
10 Questions 30 seconds per question
Chapter 17.2 Quiz
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A. HertzB. metersC. litersD. Decibels
#1- What is the EM Wave measured in?
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A. By Anton van LuewenhookB. By looking at subatomic particles
C. By accidentD. None of the above
#2 – How was the microwave discovered?
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A. Periodic TableB. Electromagnetic RealmC. InstagramD. Electromagnetic Spectrum
#3- The chart the gives us a range of all of the EM frequencies is called ____________.
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A. After MorningB. Amplitude MagnificationC. Amplitude ModulationD. Angry and Mean
#4- What does AM stand for?
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A. Frequency ModulationB. Fast MovingC. Frequency MovementD. Frequency Motion
#5- What does FM stand for?
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A. BlueB. YellowC. RedD. Pink
#6-Infrared Rays have a wavelength longer than ______ light.
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A. Infrared RaysB. MicrowavesC. Light RaysD. Gamma Rays
#7 – Which rays are the highest frequency EM waves?
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A. Clean stallsB. Help patients walk aroundC. Kills germ (cancer) cellsD. None of the above
#8 – Ultraviolet rays have a usage in hospitals to do what?
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A. SilverB. GoldC. LeadD. Platinum
#9 – What absorbs X Rays?
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A. Modulation
#10 – What is variation in frequency or amplitude when waves are broadcast?