This document discusses the properties and behavior of convex and concave lenses. It explains that convex lenses form real, inverted images unless the object is placed between the focal point and the lens, in which case it forms a virtual, upright image. It also explains that concave lenses always form virtual, upright images that are smaller than the object. The document provides formulas for calculating the location and size of images formed by lenses and works through two example problems.

1. Oh, and Math

2. Thicker in the middle
than the edges.
Rays converge to
focus an image.
has + focal length

3. 1. A ray parallel to the principal axis will
refract through the focal point.
2. A ray through the focal point will refract
parallel to the principal axis.
3. A ray through the center of the lens
maintains its course.

5. Lens is thinner in
the middle than
the edges.
Refracted rays
diverge on other
side of lens.
has – focal length

6. Back trace the refracted ray
Back trace the refracted ray
Back trace the refracted ray
virtual
smaller
upright

8. Convex Lens: Real image unless object is
in front of F, then virtual image is formed.
Inverted unless in front of F, then upright
image is formed.
Farther away object is smaller image is.
Bring in closer then image is enlarged. And
when object is in front of F, huge and
same side as F.

9. Concave Lens: Image is Virtual, smaller
and Upright. Also, on same
side of lens as object.

10. Same Formula: 1 + 1 = 1
do di f
m = hi = -di
ho do

11. 1. A 18-cm tall object is placed 33 cm from a converging
lens that has a focal length of 10 cm.
How far from the lens will the image be formed?
How tall is the image formed?
Describe the image formed.
2. The same 18-cm tall object is now placed 33 cm from a
diverging lens that has a focal length of -28 cm.
How far from the lens will the image be formed?
How Tall is the image?
Describe the image.