Electromagnetic Waves
E-M waves Transverse Electric field and magnetic field- both perpendicular to propagation of the wave Can travel through a vacuum or a medium
Frequency and E-M Spectrum Oscillations of electric charges at source determine the frequency Frequency determines type of wave
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
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
Polarization Ordinary light vibrates in all planes Polarized light has a single plane of oscillation
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
Polarization by reflection When light reflects off a surface, the reflected wave vibrates most along the plane parallel to the surface
Pairs of polarizing filters
Uses of polarization Polarized sunglasses can be used to block the polarized glare (reflection) off a surface such as glass or water
Polarizing filter
Speed of Light 3.80x108m/s In a vacuum, is a constant “c” In one year light travels 9.46x1012 km = 1 light year
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
Wave Nature of Light Some diffraction (not as strong as sound)- that’s why shadows have blurry edges Reflection Refraction Wavelength Doppler effect
Color White light is combination of colors Color of light is property of its wavelength
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