Click the [b]play[/b] button to find out how image were formed.
What will happened to the image, if part of the ligh path were blocked. (Click the [b]block[/b] button)
Press the Alt key and the left mouse button to drag the applet off the browser and onto the desktop.
It only reduced the intensity of the image. You can drag any one of the dot in the simulation to change its setting.