electromagnetcetera… chapter 18. electromagnetic waves constantly changing fields: –electric...
DESCRIPTION
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 spaceTRANSCRIPT
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.
*Electromagnetic Radiation – transfer of energy by EMW through matter or space
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
Wave or Particle?
WAVE =-Thomas Young (P. 536)
-Experiment showed bands of interference
PARTICLE =-photoelectric effect -Einstein (photons – packets of energy)
Phillip Lenard – experimented/coined term…
Intensity
• Light (photons) travel outward from source in ALL directions.– Intensity decreases as light
travels farther…
Electromagnetic Spectrum
Radio Waves• Amplitude Modulation –
amplitude is varied (AM stations)
• Frequency Modulation – frequency varied(FM stations)
(Television)
**Radio waves = longest waves
• Microwaves– Cook food– Cell phones
• Radar– Cops– Baseball
Infrared Rays
• Used to discover sources of heat and heat differences– Marijuana (heat
lamps)• Heat source
– Fast food
Visible Light
• Only light human eye can see.
Ultraviolet Rays
• Source of vitamin D• Medicine, agriculture
(greenhouses)
• UVA, UVB?• Wear sunscreen?
X-Rays
• Can penetrate matter that light can’t.
• Medical, dental x-rays• Airport, courthouses,
etc.
Gamma Rays
• Shortest wavelengths• Overexposure =
death• Treat cancer -
radiation
Light Behavior
• Transparent• Translucent• Opaque
Reflection
• Regular – mirror
• Diffuse– rough surface
Refraction
Light bends or curves
Polarization
• Polarized light vibrates in one plane– Vertical or horizontal
• Sunglasses• Car visors
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…