These 3 principal rays which all start at the tip of the object (in this case, a picture of a pencil) are i. A line drawn to the center of the lens Goes straight through a lens It will reflect off a mirror according to angle in = angle out ii. A line drawn parallel to the optical axis a. in a lens It will be refracted (bent) to the opposite (right side) focus for a converging lens It will be refracted away from the back (left) focus for a diverging lens b.in a mirror It will be reflected back to the back (left) focus for a converging mirror It will be reflected away from the opposite (right) focus for a diverging mirror iii. A line drawn through the left focus (if possible) will be: Bent parallel to the optical axis (converging lens only) Reflected parallel to the optical axis (converging mirror only) 2. Move the object (the pencil on the left) around a little (right and left along the dotted line, the optical axis, not too much up and down - you can lock this with the lock symbol in the top right corner). Verify that the 3 rays of light you see are in fact the three described above. Comments? a.Where the three rays of light meet again on the right side is another pencil, this is the image