The following are suggestions for initial investigations on the optical bench. The investigations A-D start with the four setups obtained through links on the applet page. Click on the thin lens setup. By moving the cursor to the respective positions on the principal axis, record the object, lens and image positions. From your measurements obtain the object and image distances.
Lateral magnification is the ratio of image height to object height.
Compare this ratio to the image distance to object distance ratio. If so, measure their positions on the principal axis and obtain an estimate of the focal length. Now drag the lens to the new imaging position and repeat steps 1 through 5 to obtain a second set of data. First study the simulations obtained by clicking on the higher index and lower index links. Drag the lens well inside the dielectric and observe which of the setups higher or lower index corresponds to the present simulation.