1. Electromagnetic Waves

2. E-M waves
Transverse
Electric field and magnetic field- both perpendicular to propagation of the wave
Can travel through a vacuum or a medium

3. Frequency and E-M Spectrum
Oscillations of electric charges at source determine the frequency
Frequency determines type of wave

5. Diffraction Bending around an obstacle Depends on the wavelength!
Try diffraction in sound with a fan- if a sound diffracts well, it will be constant. If it doesn’t diffract well, a fan will make it sound like pulses

6. Polarization Most Light Sources Are Not Like This
They Normally Consist of Waves In A Variety of Orientations
This Is How They Would Look In A Head-On and an Oblique View 6

7. Polarization Ordinary light vibrates in all planes
Polarized light has a single plane of oscillation

8. Polarization by filtering
Polarizing filters contain long molecules where electrons only vibrate in one plane- only allow light waves vibrating in that plane to pass through

9. Polarization by reflection
When light reflects off a surface, the reflected wave vibrates most along the plane parallel to the surface

10. Pairs of polarizing filters

11. Uses of polarization
Polarized sunglasses can be used to block the polarized glare (reflection) off a surface such as glass or water

12. Polarizing filter

13. Speed of Light 3.80x108m/s In a vacuum, is a constant “c”
In one year light travels 9.46x1012 km = 1 light year

14. Speed of Light
Astronomy is like looking back in time- light that we see from distant stars left those stars long ago
The light from our sun takes about 9 minutes to reach us
If we look at the most distant stars, we are looking at history closer to the big bang

15. Wave Nature of Light
Some diffraction (not as strong as sound)- that’s why shadows have blurry edges
Reflection
Refraction
Wavelength
Doppler effect

16. Color White light is combination of colors
Color of light is property of its wavelength

17. Color by addition Red, green, blue are primary colors
Combine all 3 primary colors= white light
Combine any pair of primary colors = secondary color
Yellow, cyan, magenta