unit 1

unit 1

1. WAVES (not like the ones you'll be riding in summer!!)

   • sound/water
     • seismic - p waves, s waves.
       • p-waves travel through solid and liquid parts of the earth, travel very fast, same direction the wave is moving, example of longitudinal wave
       • s-waves travel very fast but slower than p waves, only able to travel through solid parts of the earth, at right angles to direction, they are transverse waves
       • seismographs - evidence about structure, after earthquakes, s-waves are only detected in certain parts of the earth, s-waves stopped by outer core
     • v=wavelength x frequency
   • made up of a series of oscillations, in transverse oscillations are at right angles to the direction of movement.
   • experiments
     • diffraction - spreading out when pass through a gap or object, depends on size of gap or wavelength size, smaller the gap or longer the wavelength the more it spreads out
     • refraction - travel at different speeds in different densities, so when it crosses a boundary it either speeds up or slows down, to a denser medium it slows down, and vis versa. only refracted if they meet at a new ambler, if they travel along the normal they just speed up, and do not diffract.
     • reflection - if angle is less than critical angle (most light is refracted but some is internally reflected) equal to critical angle (along the surface but a lot of internal reflection) greater that the critical angle ( no light comes out, it's all internally reflected
   • monochromatic
     • intense beam, in "phase", lasers.
       • used on blue ray, cds and dvds.
         • laser is reflected from shiny bottom of cd, lands in pit and is detected by a light sensor that turns into electrical signal
   • electromagnetic
     • spectrum
       • atmosphere
         • infared radiation, ultra violet
           • suntan, skin cancer, cataracts
             • ozone blocks uv radiation
       • • need to be in direct sight of transmitter, radiowaves don't bend around hills of through buildings oops
     • cooking
       • microwaves
         • penetrate 1cm into food, absorbed by fats and water, ke heats up the rest, conducted and convected.
       • infared
         • grills/toasters
           • radiated absorbed by surface particles of food, increasing ke, conducted or convected to more central parts

2. communication

   • wireless
     • radiowaves -->
       • for radio, tv and laptops
   • light, morse code, type of digital signal
     • 'on' or 'off', digital = multiplexing and more information, sound isn't recognised so no interference
   • fibre optics
     • total internal refection
       • very narrow core, protected, greater than critical angle, telephones and internet
         • very quick and ->
   • analogue
     • lots of noise

3. thermal energy

   • transfer
     • radiation - from sun, straight lines from the sun, at speed of light, doesn't need a medium, also occurs in vacuum, only occur through transparent substances, amount of radiation emitted or absorbed depends on surface colour and temperature
     • convection - heating a fluid (gas/liquid) heat particles, and the more energetic particles move from the hotter region to the cooler region (as they are less dense) , and take energy with them, and this then heats up the cooler one, there is circulation
     • conduction - the process where vibrating particles pass on extra kinetic energy to neighbouring particles, causes rise in temperature, as heat and kinetic energy is transferred ( from hot to cold )
   • energy loss in homes
     • insulation, tank jackets, cavity walls, draught proofing, double glazing
       • thermograms
         • white/yellow/red = hot, black/purple/dark blue = cold
   • energy = mass x specific latent heat energy = mass x specific heat capacity x temp change

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