Light. EM Waves have many uses EM Waves have different frequencies.

17.2 NotesLight

EM Waves have many uses

EM Waves have different frequencies

Electromagnetic Waves

Range of all EM frequencies

Electromagnetic Spectrum

Electromagnetic Spectrum

Measured in Hertz – one cycle per second

Measuring EM Waves

Radio Waves (Low Frequencies)MicrowavesVisible Light Infrared LightUltraviolet LightX-RaysGamma Rays (high frequencies)

Types of EM Waves

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

◦Radio WavesDef. – Longest wavelength and lowest freq.

Uses – Radio, TV

Radio Waves

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)

Infrared Rays◦Infrared RaysDef – Light rays with longer wavelength than red light.

Uses: Cooking, Medicine, T.V. remote controls

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”

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!

Infrared Light Examples

Infrared Light Examples

Old Faithful Yellowstone Park

What is this?

What do you see here?

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.

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.

Gamma Rays

◦Gamma raysDef. Highest frequency EM waves; Shortest wavelength. They come from outer space.

Uses: cancer treatment.

Clear Your Desks except for one piece of paper.

10 Questions 30 seconds per question

Chapter 17.2 Quiz

A. HertzB. metersC. litersD. Decibels

#1- What is the EM Wave measured in?

A. By Anton van LuewenhookB. By looking at subatomic particles

C. By accidentD. None of the above

#2 – How was the microwave discovered?

A. Periodic TableB. Electromagnetic RealmC. InstagramD. Electromagnetic Spectrum

#3- The chart the gives us a range of all of the EM frequencies is called ____________.

A. After MorningB. Amplitude MagnificationC. Amplitude ModulationD. Angry and Mean

#4- What does AM stand for?

A. Frequency ModulationB. Fast MovingC. Frequency MovementD. Frequency Motion

#5- What does FM stand for?

A. BlueB. YellowC. RedD. Pink

#6-Infrared Rays have a wavelength longer than ______ light.

A. Infrared RaysB. MicrowavesC. Light RaysD. Gamma Rays

#7 – Which rays are the highest frequency EM waves?

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?

A. SilverB. GoldC. LeadD. Platinum

#9 – What absorbs X Rays?

A. Modulation

#10 – What is variation in frequency or amplitude when waves are broadcast?