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 10 8 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…