2. The Electromagnetic Spectrum April 3, 20007

3. 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 InfraredUltraviolet Visible X-Ray Gamma Larger Waves Smaller Waves

4. 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)

5. 300,000 km/s (fast!) **As far as we know, NOTHING travels faster than the speed of light!! Very fast compared to the speed of sound (.340 km/s)

6. Spectrum Spectrum: 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 frequency Short wavelength = High frequency

7. ALL electromagnetic waves travel at the same SPEEDALL electromagnetic waves travel at the same SPEED

8. Frequency Increases & Wavelength Decreases!

9. Lowest frequency and longest wavelength; used for communication. 1. RADIO WAVES

10. LONGVery LONG 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 FYI!!

11. A higher energy radio wave; used for cooking food

12. 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 FYI!!

13. 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 FYI!!

14. Can’t be seen, but can be felt as heat. 2. INFRARED WAVES Everything gives off infrared radiation; it depends on the thermal energy

15. 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 FYI!!

16. Primary source of Infrared Radiation is heat or thermal radiation Any object that has a temp. radiates in the infrared, even ice cubes Ex. Charcoal is not burning but will emit heat Just FYI!!

17. 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 interpret Just FYI!!

18. CAN Part of the spectrum you CAN see. R O Y G B I V 3. VISIBLE LIGHT The color of visible light depends on its frequency

20. Present in sunlight and have enough energy to kill living cells 4. Ultraviolet Light (UV)

21. 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 FYI!!

22. Ozone absorbs highest energy UV light UV Light can cause sunburns and eventually malignant melanomas

23. Enough energy to pass through most materials (skin) 5. X-Rays Lead is one material that X – Rays cannot pass through

24. 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 FYI!!

25. 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 FYI!!

26. 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 FYI!!

27. Highestall Has the Highest energy of all of the electromagnetic waves 6. Gamma Rays Emitted by radioactive materials Used to treat cancer, Can go through concrete!

28. 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 FYI!!

29. 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 rays  A special camera is used to take pictures  The patient isn’t injured by the radiation because they quickly breathe out all the gas Radiotherapy Treatment of cancer Just FYI!!