Core Physics - Topic 1 Visible Light & The Solar System

    Copernicus - HELIOCENTRIC                  Ptolemy - GEOCENTRIC

• Ptolemy - GEOCENTRIC
  • Sun, Moon and planets move in orbits
  • Everything obits the Earth
• Copernicus - HELIOCENTRIC
  • Moons orbit the planets
  • Planets obit the Sun
• Telescopes improved - Planets discovered
  • Uranus, Neptune and Pluto

• Luminous objects in space give out visible light
  • Travels as waves of energy
  • Visible light waves allow studying of distant objects
• Objects in space give out other types of waves
  • e.g. radiowaves and microwaves

• Light travels in straight lines but can change direction
• Change in direction - REFRACTION
  • Occurs at the interface between 2 materials

• A lens is shaped so its interface changes directions of parallel light waves
• A converging/convex lens
  • curved on both sides making a thicker middle
  • light rays enter and come together - converge
  • focuses the rays
• Distance between focus and lens = focal length

Traverse waves - particles move at right angles to the direction wave is travelling
Longitudinal waves - particles move back and forth in the direction wave is travelling

• Electromagnetic waves
  • Light, radio waves, microwaves
  • Traverse
  • Do not need a medium to travel through
• Seismic waves
  • Earthquakes, explosions
  • Longitudinal or traverse
  • Travel through the Earth
• Sound waves
  • Longitudinal

• Wave frequency
  • Number of waves passing a point each second
  • Measured in hertz (Hz)
  • 1 Hz = 1 wave per second
• Wavelength
  • Distance from a point on one wave to the same point on the next
  • Measured in meters
• Amplitude
  • Maxium distance of a point on the wave from its rest position
  • Measured in meters

• Wave speed
  • How fast the energy in a wave travels

Wave speed (m/s) = distance(m)                v = x
                                    time(s)                        t

Wave speed (m/s) = frequency (Hz) x wavelength (m)        v = ⨍ x λ