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Electromagnetic Waves

Electromagnetic Waves. Remember: EM waves don’t require a medium to travel through! All travel at the speed of light (c = 3 x 10 8 m/s). Electromagnetic Spectrum. Radio. Used for transmission of data . (AM/FM Radio, TV) Radio waves are also emitted by stars and gases in space .

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Electromagnetic Waves

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  1. Electromagnetic Waves

  2. Remember: EM waves don’t require a medium to travel through! • All travel at the speed of light (c = 3 x 108 m/s)

  3. Electromagnetic Spectrum

  4. Radio • Used for transmission of data. (AM/FM Radio, TV) • Radio waves are also emitted by stars and gases in space. • Large wavelengths: anything bigger than 30 cm

  5. Microwave • Microwave radiation can generate thermal energy (heat). • Applications: microwave ovens, radar, aircraft navigation • Also used by astronomers to learn about the structure of nearby galaxies. • Wavelengths: 30 cm – 1 mm

  6. Infrared (IR) • Most anything will radiate IR due to thermal agitation of its molecules. (Heat it up and it will emit IR… used in 1st gen of night vision goggles) • Applications: infrared photography, molecular vibrational spectra • Wavelengths: 1 mm – 700 nm

  7. Sir Frederick Herschel IR discovery

  8. Visible Light • What our eyes can detect. • Red: 700 nm – 620 nm • Orange: 620 nm – 585 nm • Yellow: 585 nm – 570 nm • Green: 570 nm – 490 nm • Blue: 490 nm – 440 nm • Indigo: 440 nm – 420 nm • Violet: 420 nm – 400 nm Remember your buddy, Roy G. Biv

  9. Ultraviolet (UV) • Ultraviolet radiation is emitted by the Sun and are the reason skin tans and burns. • Applications: sterilizing medical instruments, identification of fluorescent minerals. • "Hot" objects in space emit UV radiation as well. • Wavelengths: 400 nm – 60 nm

  10. X-Rays • Applications: medical examinations of bones, teeth, vital organs. Treatment for types of cancer. • Hot gases in the Universe also emit X-rays. • Wavelengths: 60 nm – 10-4nm

  11. Gamma Rays • Applications: examination of thick materials for structural flaws, treatment for typed of cancer, food irradiation, making Hulk. • The biggest gamma-ray generator of all is the Universe. • Wavelengths: 0.1 nm – 10-5 nm

  12. Acronyms that may help • Rotten Men Invariably Visit Ugly X Girlfriends or • Rattlesnakes May Inject Venom Under XtremeaGitation

  13. Speed in a vacuum is c • c = 3x108m/s • Higher f  more energetic • Lower f  less energetic c = fλ

  14. So why do we only see a tiny bit of the spectrum?

  15. Visible Light Spectrum: refers to that narrow wave of frequencies that we can see.

  16. If we shine light through a prism, we can separate out the colors. • This is known as dispersion • Visible light with all the colors mixed in is usually called white light.

  17. How do we see color? • Light enters pupil, hits the retina. • The retina has a bunch of light sensing cells called rods and cones. • Rods sense the intensity of the light. • Cones detect the color (wavelength). • Chemical reaction is started, sending signals along the nerves to the brain.

  18. White light means that all 3 color-specific cones are activated. • Yellow means that green and red cones are activated. • And so on.

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