Convex Lens

• What is the shape of a convex lens?


  Convex lenses are thicker at the center than at the edges
• What is the key feature of all lenses?


  They refract light
• What happens to light rays when they pass through a convex lens?


  They bend towards the normal when entering and away from the normal when exiting
• What do we call the point where light rays focus after passing through a convex lens?


  The principal focus
• What happens to light rays when they pass through a convex lens?


  They bend towards the normal when entering and away from the normal when exiting
• What is the symbol for the principal focus?


  Capital F
• What is the distance from the center of the lens to the principal focus called?


  The focal length
• How does the strength of a convex lens affect its focal length?


  Different convex lenses have different focal lengths depending on their strength
• How do you produce ray diagrams for a convex lens?


  1. Place the object at least two focal lengths away from the lens.
  2. Draw a line from the top of the object through the center of the lens.
  3. Draw another line from the top of the object parallel to the principal axis.
  4. The second line refracts through the principal focus.
  5. The intersection shows the top of the image.
• What are the three key features of an image formed by a convex lens when the object is more than two focal lengths away?


  The image is diminished, inverted, and real
• What happens to the image when the object is placed between one and two focal lengths from the lens?


  The image is magnified, inverted, and real
• What are the properties of images formed by convex lenses based on object distance?

  • Object > 2 focal lengths:
  • Image is diminished, inverted, and real
  • Object between 1 and 2 focal lengths:
  • Image is magnified, inverted, and real
• How does the strength of a convex lens affect its focal length?


  Different convex lenses have different focal lengths depending on their strength
• How do you produce ray diagrams for a convex lens?


  1. Place the object at least two focal lengths away from the lens.
  2. Draw a line from the top of the object through the center of the lens.
  3. Draw another line from the top of the object parallel to the principal axis.
  4. The second line refracts through the principal focus.
  5. The intersection shows the top of the image.
• What are the three key features of an image formed when the object is more than two focal lengths away from the lens?


  The image is diminished, inverted, and real
• What does it mean for an image to be real?


  The rays actually meet at a point
• What happens to the image when the object is placed between one and two focal lengths from the lens?


  • The image is larger than the object (magnified).
  • The image is inverted (upside down).
  • The image is real (rays meet at a point).
• How can you tell if an image is inverted?


  The image appears upside down compared to the object
• How does the distance between the object and the lens affect the properties of the image?


  If the object is more than 2 focal lengths away, the image is diminished; if between 1 and 2 focal lengths, the image is magnified
• Symbol for a convex lens