Lens / Mirror Applet

http://www.phys.hawaii.edu/~teb/java/ntnujava/Lens/lens_e.html

Recall:

Lenses:
+f, convex lens (can form both real and virtual images, depending on do)
-f, concave lens (forms ONLY virtual images, since light rays always diverge)

Mirrors
+f, concave mirror (can form both real and virtual images, depending on do)
-f, convex mirror (forms ONLY virtual images, since light rays always diverge)

1/f = 1/di + 1/do

f = (theoretical) focal length
di = image distance (where image forms)
do = object distance (where object is located, relative to lens or mirror)

-di indicates a virtual image
+di indicates a real image

mag = -di/do

-mag indicates upside-down image
+mag indicates right-side up image

If absolute value of mag is > 1, image is larger than object.
If absolute value of mag is < 1, image is smaller than object.