light

• White light


  Made up of a spectrum of different colours
• Splitting up white light

  1. Using a prism

  2. Light is refracted

  3. Light is spread out into its different colours (dispersion)
• Isaac Newton first carried out experiments with prisms and light
• Primary colours of light

  Red, green, blue
• Secondary colours of light

  Magenta, cyan, yellow
• Combining primary colours of light

  1. Red + blue = magenta

  2. Green + blue = cyan

  3. Red + green = yellow

  4. Red + green + blue = white
• Theatres use red, green and blue stage lights to produce a wide range of different colours
• Light


  The light that we see is made up of many different colours
• Primary colours


  • Red
  • Green
  • Blue
• Primary colours can be combined in different ways to make every other colour
• Colour of an object


  Determined by the wavelength of light that it reflects
• Dispersing white light


  Using a prism to split (or disperse) white light into a spectrum of colours: red, orange, yellow, green, blue, indigo and violet
• Higher frequencies of light


  Seen as blue or violet
• Lower frequencies of light


  Seen as red and orange
• Green light is in the middle of the visible spectrum
• Human eyes


  Only detect three colours: red, green and blue
• By combining red, green and blue, we can perceive many different colours
• Combining colours


  • Red light and green light = yellow
  • Mixing all three = white light
• Objects


  Absorb and reflect light differently
• Lemon


  • Reflects yellow light, all other colours are absorbed
• Light and colour are fundamental for photography
• An object can have different coloured lights shone on it to bring out certain features
• Filters


  Transmit certain colours of light and absorb others
• Diffuse reflection


  The type of reflection caused by rough surfaces, which causes light rays to be reflected in all directions
• Coloured objects reflect certain colours and absorb others
• Primary colour filters


  • Red, green and blue filters each transmit a single primary colour and absorb the other two
• Primary colour filters


  • Red filter only transmits red light, absorbs blue and green
  • Blue filter only transmits blue light, absorbs red and green
  • Green filter only transmits green light, absorbs red and blue
• Secondary colour filters


  • Cyan, magenta and yellow filters transmit two primary colours and absorb the third
• Secondary colour filters


  • Cyan filter transmits blue and green, absorbs red
  • Magenta filter transmits red and blue, absorbs green
  • Yellow filter transmits green and blue, absorbs red
• White surfaces


  Reflect all colours of light
• Black surfaces


  Absorb all colours of light
• Coloured surfaces


  Reflect some colours and absorb others
• Primary coloured surfaces


  • Red surfaces reflect red, blue surfaces reflect blue, green surfaces reflect green
• Secondary coloured surfaces


  • Reflect the two primary colours that make up that secondary colour