Thin Converging Lens

Cards (9)

  • Principal focus: the point where rays parallel to the principal axis converge with a converging lens.
  • Focal length: distance from principle focus and the optical center.
  • Principal axis: line that goes through optical center, and the 2 foci.
  • Optical center: the center of the lens
  • Real: image can be caught on a screen
  • Virtual: image cannot be caught on a screen
  • Real image: when the object is further away from the optical centre than F' is

    A) A ray through centre of the lens passes straight through the lens.
    B) A ray parallel to the principal axis passes through the focus on the other side of the lens
    C) A ray through F’ will leave the lens parallel to the principal axis
  • Virtual Image
    • When the object is closer to the optical centre than F’ is
    • Magnifying glass: when a convex lens is used like this - an object is closer to a convex (converging) lens than the principal focus (like the diagram above), the rays never converge.
  • With a thin converging lens, the image can be:
    • Enlarged: The image is larger than the object.
    • Same size: The image is the same size as the object.
    • Diminished: The image is smaller than the object.
    • Upright: The image is in the same vertical orientation as the object.