Read the webpages Lenses and Lens equations. Then run the Optics Bench Interactive from The Physics Classroom. Maximize the simulation to full screen by clicking on the double arrow in the upper left corner of the sim image. Make sure that "Lens", "Converging", and the image of the candle flame are selected. Your screen should look like the image at the right.

1. Three rays are shown. What others are missing? Why do you think they only show these three?

2. Grab the candle and move it back and forth. Describe what happens to the image, paying particular attention to what happens as it passes through the positions 2f and f.

3. Now switch the sim to "Diverging" (in the orange bar at the upper right). Repeat the experiment you did in 2. What happens that's interesting when the object passes the positions 2f and f? How does this compare to the converging lens? Why?