Day 156 physics

Convex Lenses

Convex lenses are also called converging lenses.

  • Object is symbolized by the upward arrow
  • Real focus is on the side opposite the object
  • Virtual focus is on the same side as object
  • 2f is the same as R for a mirror
  • f is still the focus as with a mirror
  • O is the optical center
  • Convex lens creates same images as a concave mirror (sometimes, real, virtual, or nonexistent)
  • Example is a magnifying glass

Image Formation

  • When object is beyond 2f, image is real, inverted, smaller than object
  • When object is at 2f, image is real, inverted, same size as object
  • When object is at f, image is nonexistent
  • When object is between f and the lens, image is larger, virtual, and upright

Comparison to Concave Mirror

  • Concave mirrors (also converging ) yield the same image results as convex lenses.
  • The same sign rules hold for the lenses that apply to mirrors.
  • Also called “diverging
  • The only image formed is smaller, virtual, and upright

Concave Lenses

  • These cave-in in the middle and are comparable in image formation to convex mirrors
  • Use the same sign rules and equations as mirrors!