Science unit - Light

• Reflection


  When light hits a mirror and bounces away from the mirror, usually a plane mirror (flat mirror)
• Law of reflection


  • The angle of incident ray is equal to the angle of the reflected ray
• Incident ray


  The light arriving towards the mirror
• Reflected ray


  The ray going away from the plane mirror
• Normal


  The line perpendicular to the mirror
• Reflection on uneven surfaces


  • Light can be reflected by an uneven surface which results in diffuse reflection
  • The uneven surface causes light to reflect with many different angles which tends to scatter the beam
  • This type of reflection is the kind we observe off snow or fog
• Refraction


  When the light is distorted or changes perspective when it passes through a different medium
• Light goes at different speeds through different mediums which means the ray of light will change direction
• Speed of light in different mediums (km/s)

  • air: 300,000
  • water: 225,000
  • glass: 200,000
• Going from denser air to rarer air

  Bending away from the normal
• Going from rarer air to denser air

  Bending towards the normal
• Refracted ray


  The line that passes through a prism
• Transmission/transmit


  The action of the refracted ray
• Primary colours of light

  • Red
  • Blue
  • Green
• Secondary colours of light

  • Magenta (Red + Blue)
  • Yellow (Red + Green)
  • Cyan (Green + Blue)
• Red + Blue + Green = White
• Dispersion


  When a prism splits a ray of white light into a spectrum of colour
• Red light is refracted the least because it has the longest wavelength, violet is refracted the most because it has the shortest wavelength
• Objects that disperse light

  • Water
  • Prisms
• Coloured filters


  Translucent filters that filter the colours of the light
• If a specific colour filter is placed in front of a white light, only the same colour of that white light will be transmitted and the rest will be absorbed, creating heat energy
• Non-luminous


  Does not emit its own light
• Luminous


  Gives off its own light
• If a green light is reflected on a red ball/object, the ball will appear black since no light can be reflected and the green light can only be absorbed
• The Milky Way


  Our galaxy, shaped like a spiral
• Types of galaxies


  • Elliptical
  • Irregular
• Galaxies are made from stellar dust, gas, solar systems and stars
• Gravity is what holds the galaxies together - even though it is at a strength that is so high
• Asteroids


  Objects made from rocks that orbit the Sun
• Asteroids are the rocky remnants of material leftover from the formation of the solar system and its planets approximately 4.6 billion years ago
• Asteroids can be up to 975km across or as small as 2 meters across