clem_waves_lesson04_presentation 101n.ppt

electromagnetic waves

1. The Electromagnetic
Spectrum

2. The Electromagnetic SpectrumThe Electromagnetic Spectrum
The EM spectrum is the ENTIRE range of EM waves in The EM spectrum is the ENTIRE range of EM waves in
order of increasing frequency and decreasing wavelength.order of increasing frequency and decreasing wavelength.
As you go from As you go from left left  right right, the , the wavelengths get smaller wavelengths get smaller and the and the
frequencies get higherfrequencies get higher. This is an . This is an inverseinverse relationshiprelationship between wave between wave
size and frequency. size and frequency. (As one goes up, the other goes down.)(As one goes up, the other goes down.) This is because the This is because the
speed of ALL EM waves is the speed of light (300,000 km/s).speed of ALL EM waves is the speed of light (300,000 km/s).

3. Things to RememberThings to Remember
The higher the frequency, the more energy the The higher the frequency, the more energy the
wave has.wave has.
EM waves EM waves do not require media do not require media in which to travel in which to travel
or move.or move.
EM waves are considered to be EM waves are considered to be transverse waves transverse waves
because they are made of vibrating electric and because they are made of vibrating electric and
magnetic fields at right angles to each other, and to magnetic fields at right angles to each other, and to
the direction the waves are traveling.the direction the waves are traveling.
Inverse relationship between wave size and
frequency: as wavelengths get smaller, frequencies
get higher.

4. Radio wavesRadio waves: Have the longest wavelengths and : Have the longest wavelengths and
the lowest frequencies; wavelengths range the lowest frequencies; wavelengths range
from 1000s of meters to .001 mfrom 1000s of meters to .001 m
Used in: RADAR, cooking food, satellite Used in: RADAR, cooking food, satellite
transmissionstransmissions
The Waves (in order…)The Waves (in order…)

5. Infrared waves Infrared waves (heat): Have a shorter wavelength, (heat): Have a shorter wavelength,
from .001 m to 700 nm, and therefore, a higher from .001 m to 700 nm, and therefore, a higher
frequency.frequency.
Used for finding people in the dark and in TV Used for finding people in the dark and in TV
remote control devicesremote control devices
Visible lightVisible light: Wavelengths range from 700 nm (red : Wavelengths range from 700 nm (red
light) to 30 nm (violet light) with frequencies light) to 30 nm (violet light) with frequencies
higher than infrared waves.higher than infrared waves.
These are the waves in the These are the waves in the
EM spectrum that humansEM spectrum that humans
can see.can see.
Visible light waves are a very Visible light waves are a very
small part of the EM spectrum!small part of the EM spectrum!

6. ROY G. BVROY G. BV
redred
orangeorange
yellowyellow
greengreen
blueblue
violetviolet
Visible LightVisible Light
Remembering the OrderRemembering the Order

7. Ultraviolet LightUltraviolet Light: Wavelengths: Wavelengths range from 400 nm to
10 nm; the frequency (and therefore the energy) is
high enough with UV rays to penetrate living cells
and cause them damage.
Although we cannot see UV light, bees, bats, butterflies,
some small rodents and birds can.
UV on our skin produces vitamin D in our bodies. Too
much UV can lead to sunburn and skin cancer. UV rays
are easily blocked by clothing.
Used for sterilization because they kill bacteria.

8. X-RaysX-Rays: Wavelengths from 10 nm to .001 nm. : Wavelengths from 10 nm to .001 nm.
These rays have enough energy to penetrate These rays have enough energy to penetrate
deep into tissues and cause damage to cells; deep into tissues and cause damage to cells;
are stopped by dense materials, such as bone.are stopped by dense materials, such as bone.
Used to look at solid structures, such as bones and Used to look at solid structures, such as bones and
bridges (for cracks), and for treatment of cancer.bridges (for cracks), and for treatment of cancer.

9. Gamma RaysGamma Rays: Carry the most energy and have : Carry the most energy and have
the shortest wavelengths, less than one the shortest wavelengths, less than one
trillionth of a meter (10trillionth of a meter (10
-12-12
). ).
Gamma rays have enough energy to go through Gamma rays have enough energy to go through
most materials easily; you would need a 3-4 ft thick most materials easily; you would need a 3-4 ft thick
concrete wall to stop them!concrete wall to stop them!
Gamma rays are released Gamma rays are released
by nuclear reactions in by nuclear reactions in
nuclear power plants, by nuclear power plants, by
nuclear bombs, and by nuclear bombs, and by
naturally occurring naturally occurring
elements on Earth.elements on Earth.
Sometimes used in the Sometimes used in the
treatment of cancers.treatment of cancers.

10. Gamma RaysGamma Rays
This picture is a This picture is a
“scintigram” “scintigram” 
It shows an asthmatic It shows an asthmatic
person’s lungs.person’s lungs.
The patient was given a slightly radioactive gas to The patient was given a slightly radioactive gas to
breath, and the picture was taken using a gamma breath, and the picture was taken using a gamma
camera to detect the radiation. camera to detect the radiation.
The colors show the air flow in the lungs.The colors show the air flow in the lungs.

11. Micro Worlds, Lawrence Berkeley National Laboratory.
http://www.lbl.gov/MicroWorlds/ALSTool/EMSpec/EMSpec2.html
Image SourcesImage Sources
NASA http://spaceplace.nasa.gov/blue-sky/
NASA
http://science-edu.larc.nasa.gov/EDDOCS/Wavelengths_for_
Colors.html
NASA http://missionscience.nasa.gov/ems/11_xrays.html
Andy Darvill, Broadoak Community School, Radioactivity Uses
http://www.northallertoncoll.org.uk/science/Additional%20Physics/
Nuclear/Nuclear/Radioactivity/uses.htm
2004 Microsoft Corporation, One
Microsoft Way, Redmond, WA
98052-6399 USA.