images in lenses

• what is the emergent ray?

  the light ray that leaves after refraction
• since the light is refracted twice as it passes through the lens, a little bit is displaced sideways. what does this depend on?

  the thickness of the material
• in this study we assume lenses are so thin that little sideways displacement occurs
• CONVERGING LENSES RULES

  1. a ray parallel to the principle axis is refracted through the principle focus
  2. a ray through the secondary focus is refracted parallel to the principle axis
  3. a ray through the optical centre continues on its path
• CONVERGING LENSES RULES

  1. if an object is located beyond 2F', the image will be: smaller, inverted, located between F and 2F, and real
  2. if an object is located at 2F', the image will be: same size, inverted, located at 2F, and real
  3. if an object is located between F' and 2F', the image will be: larger, inverted, located beyond 2F, and real
  4. if an object is located at F', there is no image
  5. if an object is located before F', the image will be: larger, upright, located behind the lens, and virtual
• DIVERGING LENSES RULES

  1. a ray parallel to the principle axis is refracted like it came through F
  2. a ray that appears to go through F' is refracted parallel to the principle axis
  3. a ray through the optical centre continues on its path
• a diverging lens always forms a smaller, upright, virtual image on the same side of the lens as the object