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CP Physics Ms. Morrison
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Moving charged particles create magnetic fields Changing motion of charged particle creates expanding and collapsing magnetic field which generates and expanding and collapsing electric field Travel at 3.0 x 10 8 m/s through empty space ( c = speed of light) Travels more slowly through mediums Energy depends on frequency
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1. Radio Waves 2. Microwaves 3. Infrared waves 4. Visible light 5. Ultraviolet light 6. X-rays 7. Gamma rays
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Lowest frequency Longest wavelength Least energy of spectrum Carry sound waves
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Frequencies match natural frequencies of molecules (fats, proteins, etc.) Causes food molecules to vibrate making the food cook itself Icebergs give off microwaves Match natural frequencies of some pacemakers
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Heat waves – all animals give off infrared Uses: Heat lamps Night vision Alcohol breath test Remote controls
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Only 1/1,000,000 of EM spectrum Different frequencies seen as colors (ROY G BIV) Red light Lowest frequency (least energy) Longest wavelength Violet light Highest frequency (most energy) Shortest wavelength
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Causes sunburns, damages tissues, and can kill bacteria UV-B rays more dangerous than UV-A because they have higher frequency
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Produced by high speed electrons slamming into a metal plate Uses: Medical X-rays (bones, teeth) Airport security
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Highest frequency of EM spectrum so highest energy waves of spectrum and greatest penetrating power Shortest wavelengths of spectrum Produced by nuclear particles and occur with every nuclear reaction Used in radiation therapy (kill healthy cells, but kill cancer cells)
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Frequencies that eye is sensitive to c = 3 x 10 8 m/s c = λ f Transverse wave Interaction with materials Transparent – all light transmitted, ex. Clear glass Translucent – scatters light transmitted, ex. Frosted glass Opaque – does not transmit any light, ex. Brick
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Behaves like wave when traveling through empty space or through a medium when it does not interact with the medium’s particles Behave like all other waves: Reflects Refracts Diffracts (ex. Prism – see colors of light) Interferes Constructive – produces light bands Destructive – produces dark bands
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1900s – discovered that light can act like a particle when it interacts with matter Certain colors of light produce photosynthesis when light absorbed by green leaves Certain colors of light shown on metal plates cause electrons to jump of the atoms and create electric current (ex. Solar calculators) Electrons jump to higher energy levels in atom when absorb energy, when return to ground level will emit specific color of light
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Explains how light interacts with matter Photon = quantum of light energy (packet of light energy) Photon’s energy depends on its frequency – red photons have less energy than violet photons Dual Theory of Light: Light moves through space as a wave and interacts with matter as a particle
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Illuminated objects = reflect light, ex. Moon Luminous objects = emit light, ex. Sun Different methods to produce light based on how they excite electrons: Heating gases Heating metal filaments Electricity Ultraviolet radiation Chemoluminescence Bioluminescence Phosphorescence
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Only occurs with transverse waves Polarized materials have molecules that only allow EM waves of one direction pass through them = polarizing axis Blocks waves perpendicular to polarizing axis Example, polarized sunglasses reduce glare of light reflecting off a variety of surfaces
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