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Electromagnetcetera…

Electromagnetcetera…. Chapter 18. Electromagnetic Waves. Constantly changing fields: Electric field Magnetic field. EMW’s. Produced when electric charge vibrates or accelerates ***Do NOT need a medium to travel in.

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Electromagnetcetera…

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  1. Electromagnetcetera… Chapter 18

  2. Electromagnetic Waves • Constantly changing fields: • Electric field • Magnetic field

  3. EMW’s • Produced when electric charge vibrates or accelerates ***Do NOT need a medium to travel in. *Electromagnetic Radiation – transfer of energy by EMW through matter or space

  4. Speed of EMW’s • In a vacuum… ALL EMW’s travel same speed. c = 3.00 X 108 m/s • EMW’s vary in wavelength and Hz. • S = W X F

  5. Wave or Particle? WAVE = -Thomas Young (P. 536) -Experiment showed bands of interference PARTICLE = -photoelectric effect -Einstein (photons – packets of energy)

  6. Phillip Lenard – experimented/coined term…

  7. Intensity • Light (photons) travel outward from source in ALL directions. • Intensity decreases as light travels farther…

  8. Electromagnetic Spectrum

  9. Radio Waves • Amplitude Modulation – amplitude is varied (AM stations) • Frequency Modulation – frequency varied (FM stations) (Television) **Radio waves = longest waves

  10. Microwaves • Cook food • Cell phones • Radar • Cops • Baseball

  11. Infrared Rays • Used to discover sources of heat and heat differences • Marijuana (heat lamps) • Heat source • Fast food

  12. Visible Light • Only light human eye can see.

  13. Ultraviolet Rays • Source of vitamin D • Medicine, agriculture (greenhouses) • UVA, UVB? • Wear sunscreen?

  14. X-Rays • Can penetrate matter that light can’t. • Medical, dental x-rays • Airport, courthouses, etc.

  15. Gamma Rays • Shortest wavelengths • Overexposure = death • Treat cancer - radiation

  16. Light Behavior • Transparent • Translucent • Opaque

  17. Reflection • Regular • mirror • Diffuse • rough surface

  18. Refraction Light bends or curves

  19. Polarization • Polarized light vibrates in one plane • Vertical or horizontal • Sunglasses • Car visors

  20. Scattering • Light is redirected as it passes through a medium • Why is the sky blue? • Blue light scatters the most… filling the sky… to make it appear blue… but…

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