1. Light and Electromagnetic Waves
              
                                                                                           
            
            

2. Electromagnetic Waves
Consist of two transverse waves that are at right angles to one another
Electric Field
Magnetic Field

3. Electromagnetic Waves
Do not need a medium to transfer energy
Will travel through space!
Speed in a vacuum = 3.0 x 108 m/s

4. The Electromagnetic Spectrum
EM waves are arranged according to wavelength and frequency
Long wavelengths have Low frequencies
Short wavelengths have High frequencies

5. The Electromagnetic Spectrum

6. The Electromagnetic Spectrum

7. Radio Waves Lowest Frequency, Lowest Energy Waves
Modulation: Variation in either frequency or amplitude of a wave

8. Microwaves Higher frequency radio wave
Microwave ovens – microwaves penetrate food and vibrate water & fat molecules to produce thermal energy
Also used in cell phones and radar (speed gun and weather forecasting- Doppler Radar)

9. Microwaves

10. Infrared Can not see, but felt as Heat
Depends on temperature of object
50% of sun’s rays are infrared
Infrared Lamps and Cameras (thermographs)

11. Visible Light
Very small part of the spectrum we can see called visible light. Wave length (from 400 nm to 700 nm)
Almost ½ the sun’s rays are in visible light
Required for photosynthesis in plants

12. Ultraviolet Frequencies just higher than visible light
Energy from these rays can kill living cells (good & bad)
Used in food preparation and storage
Ozone in the atmosphere and Melanin in our skin help protect us from UV rays.

13. Ultraviolet
How are we destroying the ozone layer?

14. X-Rays Greater energy than UV rays. Shorter wave lengths
Can pass through less dense material (skin tissue) and is absorbed by more dense material (bone)

15. Gamma waves Highest frequencies & shortest wavelengths
Highest Energy, can pass
through skin and bones
Radioactive materials &
nuclear explosions emit gamma rays
Can penetrate up to 3 meters of concrete!

16. Summary

17. More on Light
              
                                                                                           
            
            

18. Luminous vs. Illuminated
Luminous: Anything that gives off its own light. Produces light.
Ex. sun, stars, light bulbs, candles, fire

19. Luminous vs. Illuminated
Illuminated: Anything seen because it is lit up by another luminous object. Reflects light.
Ex. moon, paper, person

20. Luminous Lights (Gives off its own light)
Incandescent- from heated objects, exa. standard light bulb, fire
Fluorescent- gas under pressure; cool to the touch
Neon- neon gas under
pressure; cool

21. Materials and Light
Transparent: Most light passes through the material
Translucent: Scatters light; Can see light coming through, but not clearly
Opaque: Absorbs and/or reflects all light that hits it; Cannot be seen through

22. Transparent, Translucent, or Opaque

23. Transparent, Translucent, or Opaque

24. Transparent, Translucent, or Opaque

25. Transparent, Translucent, or Opaque

26. Transparent, Translucent, or Opaque

27. Transparent, Translucent, or Opaque

28. Behavior of Light Einstein discovered light has a dual nature.
Light has properties of a wave, (Can travel through vacuum of space.)
It can also behave as a particle, (Can bounce off other particles.)
Particles of light are called photons