Electromagnetic Wave CB manuscript figures updated s.ppt

CB manuscript figures updated

1. Warm UpWarm Up

1. What is energy?1. What is energy?

2. What is kinetic energy? How do you 2. What is kinetic energy? How do you
calculate it?calculate it?

3. What is potential energy?3. What is potential energy?

4. What is a transverse wave? Draw and 4. What is a transverse wave? Draw and
label. label.

5. What is a longitudinal wave? Draw and 5. What is a longitudinal wave? Draw and
label. label.

2. Electromagnetic WavesElectromagnetic Waves
     

3. Waves… a reviewWaves… a review

Most waves are either longitudinal or Most waves are either longitudinal or
transverse.transverse.

Sound waves are longitudinal.Sound waves are longitudinal.

But all But all electromagneticelectromagnetic waves are waves are
transverse…transverse…

4. ?
?

5. Nature of Electromagnetic WavesNature of Electromagnetic Waves
They are They are Transverse waves without a Transverse waves without a
medium.medium. (They can travel through (They can travel through empty empty
spacespace))
They travel as They travel as vibrations in electrical and vibrations in electrical and
magnetic fields.magnetic fields.
Speed of electromagnetic waves = speed of Speed of electromagnetic waves = speed of
light: 300,000,000 meters/secondlight: 300,000,000 meters/second
(Takes light 8 minutes to move from the sun to earth {150 million miles} at (Takes light 8 minutes to move from the sun to earth {150 million miles} at
this speed.)this speed.)

6. 
When an electric field changes, so does the When an electric field changes, so does the
magnetic field. When one field vibrates—so does magnetic field. When one field vibrates—so does
the other.the other.

RESULT-RESULT-

An An electromagneticelectromagnetic
wave.wave.

Click here Click here Animation: Interaction of vibrating Animation: Interaction of vibrating
chargescharges

7. Waves or ParticlesWaves or Particles

Electromagnetic radiation has properties of waves Electromagnetic radiation has properties of waves
but also can be thought of as a but also can be thought of as a stream of stream of
particles.particles.

Example: LightExample: Light

Light as a wave: Light behaves as a transverse Light as a wave: Light behaves as a transverse
wave which we can filter using polarized lenses.wave which we can filter using polarized lenses.

A “particle” of light is called a A “particle” of light is called a photonphoton

9. Waves of the Electromagnetic SpectrumWaves of the Electromagnetic Spectrum

Electromagnetic SpectrumElectromagnetic Spectrum—name for the range of —name for the range of
electromagnetic waves when placed in order of increasing electromagnetic waves when placed in order of increasing
frequencyfrequency

Click here Click here ((AnimationAnimation—Size of EMwaves—Size of EMwaves))
RADIO
WAVES
MICROWAVES
INFRARED
RAYS
VISIBLE LIGHT
ULTRAVIOLET
RAYS
X-RAYS
GAMMA
RAYS

11. RADIO WAVESRADIO WAVES

A. Have the A. Have the longestlongest wavelengths and wavelengths and
lowest lowest frequencies of all the frequencies of all the
electromagnetic waves.electromagnetic waves.

B. A radio picks up radio waves through an B. A radio picks up radio waves through an
antenna and converts it to antenna and converts it to sound waves.sound waves.

C. Each radio station in an area broadcasts C. Each radio station in an area broadcasts
at a different frequency. # on radio dial tells at a different frequency. # on radio dial tells
frequency.frequency.

D. MRI (MAGNETIC RESONACE IMAGING)D. MRI (MAGNETIC RESONACE IMAGING)
Uses Short wave radio waves with a magnet to Uses Short wave radio waves with a magnet to
create an imagecreate an image

12. MRI of the BrainMRI of the Brain

13. AM=Amplitude modulation—waves bounce off
ionosphere can pick up stations from different
cities.
+

14. FM=Frequency modulation—waves travel in a
straight line & through the ionosphere--lose
reception when you travel out of range.
+

15. MICROWAVESMICROWAVES

MicrowavesMicrowaves—have the shortest wavelengths —have the shortest wavelengths
and the highest frequency of the and the highest frequency of the radio waves.radio waves.

Used in microwave ovens.Used in microwave ovens.

(Waves transfer energy to the water in the food causing (Waves transfer energy to the water in the food causing
them to vibrate which in turn transfers energy in the them to vibrate which in turn transfers energy in the
form of heat to the food.)form of heat to the food.)

Used by Used by cell phones and pagers.cell phones and pagers.

RADARRADAR ( (RaRadio dio DDetection etection aand nd RRanging)anging)

(Used to find the speed of an object by sending out (Used to find the speed of an object by sending out
radio waves and measuring the time it takes them to radio waves and measuring the time it takes them to
return.)return.)

17. INFRARED RAYSINFRARED RAYS

InfraredInfrared= below red= below red

Shorter wavelength and higher frequency than Shorter wavelength and higher frequency than
microwaves.microwaves.

You can feel the longest ones as warmth on your skinYou can feel the longest ones as warmth on your skin

Heat lamps give off infrared waves.Heat lamps give off infrared waves.

Warm objects give off more heat energy than cool Warm objects give off more heat energy than cool
objects.objects.
ThermogramThermogram—a picture that shows regions of —a picture that shows regions of
different temperatures in the body. Temperatures different temperatures in the body. Temperatures
are calculated by the amount of infrared radiation are calculated by the amount of infrared radiation
given off. Therefore people give off infrared rays.given off. Therefore people give off infrared rays.

18. Night vision Night vision
gogglesgoggles
Remote controlsRemote controls

19. Warm UpWarm Up

1. Draw the EM spectrum. 1. Draw the EM spectrum.

2. What is a medium?2. What is a medium?

3. Do EM waves need a medium to travel?3. Do EM waves need a medium to travel?

4. What is a “vacuum”?4. What is a “vacuum”?

5. What is a niche? Give an example.5. What is a niche? Give an example.

6. What is ecology?6. What is ecology?

20. VISIBLE LIGHTVISIBLE LIGHT

Shorter wavelength and higher frequency than Shorter wavelength and higher frequency than
infrared rays.infrared rays.

Electromagnetic waves we Electromagnetic waves we can see.can see.

Longest wavelength= red lightLongest wavelength= red light

Shortest wavelength= Shortest wavelength= violet (purple)violet (purple) light light

When light enters a new medium it bends When light enters a new medium it bends
(refracts: (refracts: we’ll talk about this tomorrowwe’ll talk about this tomorrow). Each ). Each
wavelength bends a different amount allowing wavelength bends a different amount allowing
white light to separate into its various colors white light to separate into its various colors
ROYGBIV.ROYGBIV.

22. ULTRAVIOLET RAYSULTRAVIOLET RAYS
Shorter wavelength and higher Shorter wavelength and higher
frequency than visible lightfrequency than visible light
Carry Carry more energymore energy than visible light than visible light

Used to Used to kill bacteria.kill bacteria. (Sterilization of (Sterilization of
equipment)equipment)
Causes your skin to produce Causes your skin to produce vitamin Dvitamin D
(good for teeth and bones)(good for teeth and bones)

23. Ultraviolet (cont.)Ultraviolet (cont.)
UVAUVA UVB and UVCUVB and UVC
EnergyEnergyHighest of UV Highest of UV
waves waves
Lower than UVALower than UVA
Health Health
risksrisks

Extremely low Extremely low
risk for DNA risk for DNA
damagedamage

Can destroy Can destroy
Vitamin A in skinVitamin A in skin

Can cause DNA Can cause DNA
damage, leading to damage, leading to
skin cancerskin cancer

Responsible for Responsible for
sunburnsunburn

24. X- RAYSX- RAYS
*Shorter wavelength and higher frequency*Shorter wavelength and higher frequency
than UV-raysthan UV-rays
*Carry a great amount of energy*Carry a great amount of energy

*Can penetrate most matter.*Can penetrate most matter.
Bones and teethBones and teeth absorbabsorb x-rays. (The light part of an x-ray x-rays. (The light part of an x-ray
image indicates a place where the x-ray was absorbed)image indicates a place where the x-ray was absorbed)
Too much exposure Too much exposure can cause cancercan cause cancer
(lead vest at dentist protects organs from unnecessary exposure)(lead vest at dentist protects organs from unnecessary exposure)
Used by Used by engineersengineers to check for tiny cracks in structures. to check for tiny cracks in structures.
The rays pass through the cracks and the cracks appear dark on The rays pass through the cracks and the cracks appear dark on
film.film.

26. GAMMA RAYSGAMMA RAYS

Shorter wavelength and higher frequency than Shorter wavelength and higher frequency than
X-raysX-rays

Carry the Carry the greatest amount of energygreatest amount of energy and and
penetrate the most.penetrate the most.

Used in Used in radiation treatmentradiation treatment to kill cancer to kill cancer
cells.cells.

Can be very harmful if not used correctly.Can be very harmful if not used correctly.

27. Gamma RaysGamma Rays

They are produced by the hottest and They are produced by the hottest and
most energetic objects in the universemost energetic objects in the universe, ,
such as neutron stars and pulsars, such as neutron stars and pulsars,
supernova explosions, and regions around supernova explosions, and regions around
black holes. black holes.

On Earth, gamma waves are generated by On Earth, gamma waves are generated by
nuclear explosionsnuclear explosions, , lightninglightning, and the less , and the less
dramatic activity of dramatic activity of radioactive decayradioactive decay. .

28. Using the EM waves to view the Using the EM waves to view the
SunSun
AnimationAnimation—View a Galaxy at different wavelengths—View a Galaxy at different wavelengths
Song:Song:
http://www.youtube.com/watch?v=P_PVz8HrrCI&safe=activehttp://www.youtube.com/watch?v=P_PVz8HrrCI&safe=active

29. 
Brief SUMMARYBrief SUMMARY

A. All electromagnetic wavesA. All electromagnetic waves travel at the travel at the
same speed. (300,000,000 meters/second same speed. (300,000,000 meters/second
in a vacuum.in a vacuum.

B. They all have different B. They all have different wavelengthwavelength and and
different different frequencies.frequencies.

Long wavelength-Long wavelength-lowest frequencylowest frequency

Short wavelengthShort wavelength highest frequency highest frequency

The higher the frequency the The higher the frequency the higher the higher the
energy.energy.