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Electromagnetic Radiation

Electromagnetic Radiation. Physics       Relax and Enjoy the Ride… It’s quite a ride. Waves… a review. Most waves are either longitudinal or transverse. Sound waves are longitudinal. But all electromagnetic waves are transverse…. ?. ?. Wave Relationships.

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Electromagnetic Radiation

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  1. Electromagnetic Radiation Physics  Relax and Enjoy the Ride… It’s quite a ride.

  2. Waves… a review • Most waves are either longitudinal or transverse. • Sound waves are longitudinal. • But all electromagnetic waves are transverse…

  3. ? ?

  4. Wave Relationships • Notice from the definitions we can relate the properties of a wave to one another

  5. Wave Relationships • Frequency is usually expressed in the unit of Hertz • This unit is named after a German scientist who studied radio waves • For example, if a wave has a period of 10 seconds, the frequency of the wave would be 1/10 Hz, or 0.1 Hz

  6. Note that light is always traveling at the same speed (c ~ 3 x 108 m/s) • Remember: velocity = wavelength x frequency • If frequency increases, wavelength decreases • If frequency decreases, wavelength increases

  7. Electromagnetic waves • Produced by the movement of electrically charged particles • Can travel in a “vacuum” (they do NOT need a medium • Travel at the speed of light • Also known as EM waves

  8. Wave-particle Duality • Light can behave like a wave or like a particle • A “particle” of light is called a photon

  9. Radio waves • Longest wavelength EM waves • Uses: • TV broadcasting • AM and FM broadcast radio • Avalanche beacons • Heart rate monitors • Cell phone communication

  10. Microwaves • Wavelengths from 1 mm- 1 m • Uses: • Microwave ovens • Bluetooth headsets • Broadband Wireless Internet • Radar • GPS

  11. Infrared Radiation • Wavelengths in between microwaves and visible light • Uses: • Night vision goggles • Remote controls • Heat-seeking missiles

  12. Visible light • Only type of EM wave able to be detected by the human eye • Violet is the highest frequency light • Red light is the lowest frequency light

  13. Wavelengths of Light - Visible • What we see as white light is actually made up of a continuum of components • Traditionally, we break white light into red, orange, yellow, green, blue, indigo, and violet (ROY G BIV) • There is actually a continuous transition of color, each with its own wavelength and frequency

  14. Ultraviolet • Shorter wavelengths than visible light • Uses: • Black lights • Sterilizing medical equipment • Water disinfection • Security images on money

  15. Ultraviolet (cont.)

  16. X-rays • Tiny wavelength, high energy waves • Uses: • Medical imaging • Airport security • Inspecting industrial welds

  17. Gamma Rays • Smallest wavelengths, highest energy EM waves • Uses • Food irradiation • Cancer treatment • Treating wood flooring

  18. Blackbody Radiation Cool gas ( ~60K) Young star ( ~600K) The Sun (~6000K) Hot stars in a cluster ( ~60,000K)

  19. The Sun at Different Wavelengths Visible Ultraviolet X-ray X-ray

  20. With a traditional optical telescope, the space between stars and galaxies (the background) is completely dark. However, a sufficiently sensitive radio telescope shows a faint background glow, almost exactly the same in all directions, that is not associated with any star, galaxy, or other object. This glow is strongest in the microwave region of the radio spectrum. The CMB's serendipitous discovery in 1964 by American radio astronomers Arno Penzias and Robert Wilson was the culmination of work initiated in the 1940s, and earned them the 1978 Nobel Prize.

  21. Doppler Effect • The motion of an object can be measured through a change in the frequency of the waves emitted by the object • The increase in pitch of an approaching police car is caused by the compression of the sound wave • The pitch decreases as the police car moves away

  22. Doppler Shift • In astronomy, the same effect happens to light waves • A source that is moving away will appear redder (redshift) • A source that is moving toward us will appear bluer (blueshift) • Note: Only objects moving toward or away from us (radial motion) will show this effect

  23. EM Spectrum HW: • p. 389 # 1-3, 31-35

  24. Powerpoint Credits • J. Beauchemin 2009 free online ppt

  25. Image credits • http://www.antonine-education.co.uk/New_items/MUS/images/Making6.gif • http://www.geocities.com/researchtriangle/campus/6791/einstein12.jpg • http://abyss.uoregon.edu/~js/glossary/wave_particle.html • http://www.astro.princeton.edu/~gk/A402/electromagnetic_spectrum.jpg • http://science.hq.nasa.gov/kids/imagers/ems/radio.html • http://www.nentjes.info/Palace/radio-6.gif • http://www.mobilewhack.com/motorola-h12-bluetooth-headset.jpg • http://www.stuffintheair.com/radar-real-time-weather.html • http://www.imaging1.com/gallery/images/AV%20Night%20vision%20goggles.jpg • http://www.global-b2b-network.com/direct/dbimage/50329753/Study_Remote_Control.jpg • http://www.georgiaprismaward.com/The_Prism_Story_files/PRISM%20brand%20imagemed.jpg • http://science.hq.nasa.gov/kids/imagers/ems/uv.html

  26. Image Credits • http://farm3.static.flickr.com/2385/2381723771_12548f4bd1.jpg?v=1217429879 • http://intamod.com.au/images/uv2.JPG • http://science.hq.nasa.gov/kids/imagers/ems/xrays.html • http://www.sciencelearn.org.nz/var/sciencelearn/storage/images/contexts/see_through_body/sci_media/neck_x_ray/17945-5-eng-NZ/neck_x_ray_full_size_portrait.jpg • http://www.epinion.eu/wordpress/wp-content/uploads/2008/05/airport-security1.jpg • http://science.hq.nasa.gov/kids/imagers/ems/gamma.html • http://www.aboutnuclear.org/print.cgi?fC=Food • http://www.roswellpark.org/files/1_2_1/brain_spinal/gamma%20knife%204c.jpg

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