Physics Unit 1.b

Physics Unit 1.b

1. Waves

   • Transverse
     • Sideways vibrations
     • EM waves
     • Water ripples
     • Vibrations are perpendicular to the direction of energy transfer of the wave
   • Longitudinal
     • Vibrations are parallel to the direction of energy transfer of the wave
     • Sound waves and ultrasound
     • shock waves
     • A slinky
   • Properties
     • Amplitude
       • From rest to crest or trough
     • Wavelength
       • crest to crest
     • Frequency
       • Number of waves per second
     • Reflected
       • reflection of light allows us to see objects
       • angle of incidence = angle of reflection
       • bouncing back
     • Refracted
       • changing direction
       • If travelling along normal, they will change speed but will not refract
     • Diffracted
       • spreading out
       • when pass through a gap/obstacle

2. EM Waves

   • Radiowaves
     • Radio and TV signals
       • have to be in direct sight
     • Communication
     • short waves
       • Received at long distances
       • Reflected by ionosphere
     • Long Distance
       • Diffract around surface of Earth
     • Medium wave
       • can reflect from ionosphere
   • Microwaves
     • Satellite communication
     • Mobile Phones
     • Transmitters
       • Pick up signals and transmits the signal back in a diff direction
   • Infrared
     • Remote controls
       • Emitting different patterns of infrared
         • Sends different commands to the appliance
     • Optical fibres
       • Carry data over long distances quickly
   • Visible Light
     • Photography

3. Origin of the Universe

   • Doppler Effect/Red-Shift
     • Frequency of a source moving towards you will seem higher and wavelength shorter
     • Measurements of red shift suggest galaxies are moving away from us quickl
     • more distant galaxies have greater red-shifts
       • more distant galaxies are moving away from us faster than near ones
         • universe is expanding

4. Electricity and National Grid

   • Supplies power to homes and industry
   • Boost the voltage up and keep the current low
     • A high current means more energy lost through heat in the cables
   • Step-Up transformers for an efficient transmission
   • Step-Down transformers for safety and stability
   • Power Stations - Step Up - Pylons and Cables - Step Down - Consumer
   • Overhead cables
     • Pros
       • Cheap to setup
       • Easy to repair
       • Easy to set up
       • Minimal disturbance to land
     • Cons
       • Maintenance
       • Ugly
       • Weather
       • Less reliable
   • Underground cables
     • Pros
       • Less maintenance
       • Hidden
       • Weather doesn't effect it
       • Reliable
     • Cons
       • Expensive to setup
       • hard to setup
       • lots of disturbance to land
       • Hard to repair

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