Lenses

• Lenses form by refracting light and changing its direction
• What are the two main types of lens?

  • Convex
  • concave

  
• What are the properties of a convex lens?

  • Bulges outwards
  • causes rays of light parallel to the axis to be brought together (converge ) at the principle focus
• What are the properties of a concave lens?

  • Caves inwards
  • causes parallel rays of light to spread out (diverge)
• There are three rules for refraction in a convex lens

  1. An incident ray parallel to the axis refracts through the lens and passes through the principal focus on the other side
  2. an incident ray passing through the principle focus refracts through the lens and travels parallel to the axis
  3. an incident ray passing through the centre of the lens carries on in the same direction
• There are three rules for refraction in a concave lens

  1. An incident ray parallel to the axis refracts through the lens, and travels in line with the principle focus (so it has appeared to have come from the principle focus)
  2. an incident ray passing through the lens towards the principal focus refracts through the lens and travels parallel to the axis
  3. an incident ray passing through the centre of the lens carries on in the same direction
• What image is produced from a camera or eye?

  • Inverted
  • smaller
  • real
• What image is produced from a projector?

  • Inverted
  • bigger
  • real
• What image is created from a photocopie?

  • Inverted
  • same size
  • real
• What image is produced through a magnifying glass?

  • Magnified
  • virtual
  • upright