the electromagnetic spectrum april 3, 20007 so far we have talked about mechanical waves…… but...
TRANSCRIPT
The The Electromagnetic Electromagnetic
SpectrumSpectrum
April 3, 20007
So far we have talked about Mechanical Waves……
but there are some waves that don’t need a medium to travel
through…
We call these Electromagnetic waves (such as light) that
travel throughout “matter-less” space.
Radio
Microwaves
Infrared Ultraviolet
VisibleX-Ray
Gamma
Larger WavesLarger Waves Smaller WavesSmaller Waves
Light vs. Sound• Transverse
wave•Longitudinal wave
•Does not require a medium
•Frequency tells you the color•Amplitude tells you the brightness
•Requires a medium•Frequency tells you the pitch
•Amplitude tells you the loudness (decibels)
300,000 km/s 300,000 km/s (fast!)(fast!)
**As far as we know, **As far as we know, NOTHING travels faster NOTHING travels faster than the speed of light!!than the speed of light!!•Very fast
compared to the speed of sound (.340 km/s)
SpectrumSpectrum: the full range, in this case, the full range of light waves that can be given off by excited electrons.
•Arranges light waves based on their wavelength and frequency
Long wavelength = Low frequencyShort wavelength = High frequency
• ALL ALL electromagnetic electromagnetic waves travel at waves travel at the same the same SPEEDSPEED
Frequency Increases & Wavelength Decreases!Frequency Increases & Wavelength Decreases!
Lowest frequency and longest wavelength;
used for communication.
1.1. RADIO RADIO WAVESWAVES
•Very LONGLONG wavelengths•Radio and TV waves are regulated by the FCC (Federal Communications Commission) to reduce interference
•AM Radio waves have a longer wavelength (lower frequency) •FM Radio waves have a shorter wavelength (higher frequency)
Just Just FYI!! FYI!!
A higher energy radio wave; used for cooking
food
Water and fat absorb energy carried by microwaves
When these molecules move around faster they get hotter and give off heat
Microwaves are absorbed by molecules up to 2 cm below the surface (this is why food is sometimes cold in the middle! YUK!)
Just Just FYI!! FYI!!
•Used in radar because it penetrates rain and fog•Used by Cell phones• Does not occur naturally and is made by various forms of communication technology •SETI = Search for extraterrestrial Intelligence uses this frequency to search, because it is not made naturally
Just Just FYI!! FYI!!
Can’t be seen, but can be felt as heat.
2. 2. INFRARED WAVESINFRARED WAVES
Everything gives off infrared radiation; it
depends on the thermal energy
Infrared light is even used to heat food sometimes - special lamps that emit thermal infrared waves are often used in fast food restaurants!
•Examples of Infrared waves:
TV's remote control
Fire
Radiators
Infrared film to photograph a house to reveal areas in the structure that are leaking and wasting heat
Just Just FYI!! FYI!!
•Primary source of Infrared Radiation is heat or thermal radiation
Any object that has a temp. radiates in the infrared, even ice cubesEx. Charcoal is not burning but will emit heat
Just Just FYI!! FYI!!
• How Infrared radiation is used:– Snakes in the ‘viper’ family have sensory
“pits” that detect I.R., so they can detect warm-blooded prey
– Infrared pictures can be taken using special cameras and film that detects differences in temperature• Once the pictures are taken, they assign
different brightness or false colors to them to provide a picture our eyes can interpretJust Just
FYI!! FYI!!
Part of the spectrum you CANCAN see.
R R O O YY GG B B I I VV
3. 3. VISIBLE LIGHTVISIBLE LIGHT
The color of visible light depends on its frequency
Present in sunlight and have enough energy to
kill living cells
4. Ultraviolet Light (UV)
•Invisible to the human eye
•Some insects, like bumblebees, can see them
UV Light is used:
In Tanning beds
To sterilize surgical equipment
In Food processing
Just Just FYI!! FYI!!
•Ozone absorbs highest energy UV light
•UV Light can cause sunburns and eventually malignant melanomas
•Enough energy to pass through most materials (skin)
5.5. X-Rays X-Rays
• Lead is one material that X –Rays cannot pass through
•X-rays were first observed and documented in 1895 by Wilhelm Conrad Roentgen, a German scientist
•He found them quite by accident when experimenting with vacuum tubes.
•Also can be created by a machine like those for medical x-rays Just Just
FYI!! FYI!!
•The Earth's atmosphere is thick enough that virtually no X-rays are able to penetrate from outer space all the way to the Earth's surface
•Originate in nature deep in space in the hot nebulae of stars
Just Just FYI!! FYI!!
•bones and teeth are dense and absorb more X-rays then your skin does
•silhouettes of your bones or teeth are left on the X-ray film while your skin appears transparent
When X-ray light shines on us, it goes through our skin, but allows shadows of our bones to be projected onto and captured by film
•Metal absorbs even more X-rays - can you see the filling in the image of the tooth
Just Just FYI!! FYI!!
Has the HighestHighest energy of allall of the electromagnetic waves
6. 6. Gamma RaysGamma Rays
Emitted by radioactive materials
Used to treat cancer,
Can go through concrete!
•Smallest wavelengths and possess more energy than any other wave in the electromagnetic spectrum
Produced by the hottest regions of the universe
•They are produced by:
violent events as supernova explosions or the destruction of atoms
The decay of radioactive material in space
Neutron stars and pulsars, and black holes
radioactive atoms and nuclear explosions
Just Just FYI!! FYI!!
•Medical Uses:Radioactive Tracers (put into a patients body and followed as it goes through)
A patient with lung problems can breathe in Xenon-133, a gas that emits gamma raysA special camera is used to take picturesThe patient isn’t injured by the radiation because they quickly breathe out all the gas
RadiotherapyTreatment of cancer
Just Just FYI!! FYI!!