Physics P1

Physics P1

1. LOOKING INTO SPACE

   • STARS
     • Electromagnetic radiation can tell us alot about a star.
       • The colour of it, surface Temperature...
       • THERE ARE COMPLICATIONS
         • Light pollution makes it hard to see dim objects.
         • Earth's atmosphere can absorb some light
     • Distances
       • Parallax
         • When something appears to move, when you look at it from different places
         • Stars, use parallax take pictures of the sky 6 months apart .
     • We see them as they were in the past.
       • It takes a while for light from distant stars to reach us.
   • Big bang theory
     • The universe is expanding
       • Universe is moving apart
         • Distant Galaxies moving away from us
           • The wavelength changes
             • Light becomes redder
               • THIS IS CALLED RED-SHIFT
                 • THE MORE DISTANT THE GALAXY, THE FASTER IT MOVES AWAY
                 • provides evidence that the universe is expanding
     • Every thing must have been compressed into a very small space
       • Something had to get it started
         • THE BIG BANG

2. THE CHANGING EARTH

   • Active planet
     • Rocks change over the years
       • Erosion happens
         • Something most make new rock
           • Lava from volcanoes
       • Can be estimated the age of the earth
       • Fossils provide evidence that rock is constantly forming
       • Rocks are constantly recycled
         • Eroded of cliffs, crushed at seabeds.

3. WEGENER'S THEORY OF CONTINENTAL DRIFT

   • Fossils of very similar plants- animals found on opposite sides of Atlantic ocean
     • Coastlines of Africa and S- America fitted so well together
   • He said that Africa and S-America had once been one continent
     • EVIDENCE
       • Matching layers in the rocks
       • similar fossils
       • MORE EVIDENCE
         • Found that magma rises up through the sea floor
           • creates underwater mountains.
             • symmetrical at each side
             • Sea floor was spreading
               • Few CM/ per year
         • Magnetic Orientation
           • The iron in magma, align's itself with the magnetic field
             • Every half a million years, magnetic field swaps direction
     • He thought the Earth was a 'super continent'- Pangea
   • Theory was disputed
     • People thought it was absurd.
       • He could not explain how the drifting happened (wasn't detectable)
         • He hyptothesised that tidal waves or the earths rotations
           • Geologists' proved him wrong.
     • He was not a real geologist

4. The structure of the earth

   • Earth has a
     • Crust
       • part we live on
       • Very thin
       • two types of crust
         • Oceanic
           • Water
         • Continental
           • Land
     • Mantel
       • Solid, properties
         • Can flow, very slowley
       • Radio-active decay
   • Tectonic plates
     • These move. Tectonic plates are large 'rafts'
       • Convection currents in the mantle caused by heating, causes these to move
     • Moving a few cm per year

5. Seismic waves

   • Earthquakes
     • produce wave motions
     • Seismographs measure these
   • 2 different types
     • S waves
       • S waves are transverse
         • S-waves travel only through Solids,
           • they are slower then P waves
     • P waves
       • Refract as density changes
         • P waves travel through solids and liquids
           • Faster then S waves
             • longitudinal waves
   • Curve whit increasing depth
     • Waves speed up as properties change ,.

6. Waves

   • Vibrations cause waves
   • Carry and Transfer energy
   • Wave speed
     • Frequency X Wavelength
       • Frequency=HZ
       • Wavelength=M