Ray diagrams

• What type of lenses cause light rays to diverge?

  Concave lenses
• How do we represent a concave lens in a ray diagram?

  With outwards pointing V shapes at ends
• What is the horizontal line through the middle of the lens called?

  Axis
• What are the focal points in a ray diagram?

  Points where light rays converge or diverge
• What is another name for the focal point?

  Principal focus
• What does the label '2f' represent in a ray diagram?

  Twice the distance of the focal point
• If the bottom of the object is on the axis, where will the bottom of the image be?

  On the axis as well
• What type of image is formed by a concave lens?

  Virtual image
• Why is the image formed by a concave lens always virtual?

  Because one of the rays used is virtual
• What is the first step in drawing a ray diagram for a convex lens?

  Set up the lens, axis, and focal points
• How do we represent convex lenses in ray diagrams?

  With inwards pointing V shapes at ends
• What happens to the ray passing through the middle of a convex lens?

  It continues straight without refraction
• What is the nature of the image formed by a convex lens when the object is more than two focal lengths away?

  Real and inverted image
• What happens to the image size if the object is exactly at two focal lengths?

  The image is the same size as the object
• What occurs if the object is between the focal point and the lens?

  The image will be virtual and larger
• What are the characteristics of images formed by concave lenses?

  • Always virtual
  • Upright
  • Smaller than the object
• What are the characteristics of images formed by convex lenses when the object is more than two focal lengths away?

  • Real
  • Inverted
  • Smaller than the object
• What are the characteristics of images formed by convex lenses when the object is between the focal point and the lens?

  • Virtual
  • Upright
  • Larger than the object
• What is the process for drawing a ray diagram for lenses?

  1. Set up lens, axis, and focal points
  2. Draw incident rays from the object
  3. Determine where rays cross to find the image
  4. Comment on the image characteristics