AP Physics Unit13_3: Thin Lenses

Compare converging and diverging lenses in terms of focal points and ray behavior.

• Converging Lens (e.g., bi-convex):

  • Rays parallel to axis refract through the real focus (opposite side).

  • f is positive.

• Diverging Lens (e.g., bi-concave):

  • Rays parallel to axis diverge from a virtual focus (same side).

  • f is negative.

• Key Notes:

  • Converging lenses can form real or virtual images; diverging lenses only virtual.

  • Lens equation same as mirrors, but focal length sign differs.

What are the ray-tracing rules for converging and diverging lenses?

• Converging Lens:

  1. Parallel ray → refracts through far focus.

  2. Ray through near focus → refracts parallel.

  3. Ray through optical center (O) → undeflected.

• Diverging Lens:

  1. Parallel ray → refracts away from virtual focus.

  2. Ray toward far focus → refracts parallel.

  3. Ray through O → undeflected.

• Key Notes:

  • Real images form on the opposite side; virtual images on the same side as the object.

An 11 cm object is placed 44 cm in front of a converging lens (f = 24cm). Find the image location, type, orientation, and height.

An 11 cm object is placed 48 cm in front of a diverging lens (f = −24.5 cm). Describe the image.