Lenses

• There are two main types of lenses: concave and convex.
• Convex Lens

  .A convex lens has curved edges and is wider in the middle than the edges

  .The principal focus of a convex lens is the point where all of the light rays hitting the lens parallel to the x-axis meet up

  .Convex lenses are also called converging lenses
• Convex lenses produce images that are either real or virtual. Concave lenses only produce virtual images.
• How to Draw a Convex Lens Ray Diagram

  • Draw a line from the top of the object to the lens.
  • From this point on the lens, draw a second line through the principal focus on the other side of the lens.
  • Draw a third line from the top of the object straight through the middle of the lens.
  • If the lines meet on the opposite side of the lens, this forms a real image.
  • Draw the image as a vertical arrow connecting the point where the lines cross to the principal axis.
  • If the lines do not meet (diverging rays), this forms a virtual image.
• A convex lens in ray diagrams: ^

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  v

  A concave lens in ray diagrams: v

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