Physics 1 Topic 1

Physics 1 Topic 1

1. The Solar system

   • Ptolemy a greek astronomer said that the sun and all of the planets all orbited the Earth
     • This was called the Geocentric theory
     • However another greek astronomer Copernicus said that the Earth and all of the planets orbited the Sun
       • This was called the Heliocentric theory
   • Galileo
     • Observed Jupiter's moons using a telescope
       • Then discovered that the Geocentric theory was wrong
         • The Heliocentric theory was partially correct although the planets move in eliptical (oval) shapes rather than cirular

2. Wavelength

   • Waves
     • Frequency
       • The amount of complete waves there are per second
       • Measured in Hertz (Hz)
         • 1 Hz is 1 wave per second
     • Amplitude
       • Height of the peak
     • Speed
       • How fast the wave goes
       • Measured in m/s
     • Transverse waves
       • The vibrations are at 90 degrees to the direction of travel of the wave
     • Longitudinal waves
       • The vibrations are along the same direction as the wave is travelling
   • The distance from one peak to the next
   • Formulas
     • Speed= Frequency x Wavelength
     • Wave speed= distance / time
   • Measured in metres (m)

3. Reflection and Refraction

   • Waves can be reflected
     • When a wave hits a boundary between one medium and another some of its energy is refelcted
       • The angle of reflection (r) is the same angle of incidence (i)
         • The lights reflection occurs due to the change in density- water is denser to air
   • Waves travel at different speeds in substances which have different densities
     • So when a wave crosses a boundary between two substances from glass to air it changes speed
       • As light passes from the air into the glass it slows down and causes the light ray to bend towards the normal
         • Then when the light reaches the 'glass to air' boundary on the other side of the window it's passing into a less dense medium
           • This then speeds up and bends away from the normal so some of its light is reflected at its boundary

4. Lenses

   • Converging lens
     • Definition- A converging lens is convex which means it bulges outwards
       • It causes parallel rays of light to move together to a focus
         • The focal point is where rays are hitting the lens parallel to the axis all meet
   • Focal length
     • Definition- The distance from the lens to the focal point