Lenses

• Convex lens

  Light rays enter the lens and converge (Move towards each other)
• Concave lens

  Light rays enter the lens and diverge (Move away from each other)
• Principle focus


  The point at which light rays converge or diverge
• Real image


  Can be projected
• Virtual image

  Comes from behind the lens
• Magnification

  Magnification = Image height / Object height
• Colour of opaque objects

  Determined by which wavelengths of light are absorbed and reflected
• Colour filters


  Only allow a certain range of wavelengths to pass through
• Convex lens

  Corrects far sightedness
• Concave lens

  Corrects short-sightedness