CP Physics Ms. Morrison

 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

1. Radio Waves 2. Microwaves 3. Infrared waves 4. Visible light 5. Ultraviolet light 6. X-rays 7. Gamma rays

 Lowest frequency  Longest wavelength  Least energy of spectrum  Carry sound waves

 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

 Heat waves – all animals give off infrared  Uses:  Heat lamps  Night vision  Alcohol breath test  Remote controls

 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

 Causes sunburns, damages tissues, and can kill bacteria  UV-B rays more dangerous than UV-A because they have higher frequency

 Produced by high speed electrons slamming into a metal plate  Uses:  Medical X-rays (bones, teeth)  Airport security

 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)

 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

 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

 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

 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

 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

 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