This simulation software uses Java to create Fresnel diffraction patterns.
One of the key features of Fresnel Diffraction is that it allows you to generate patterns of the shadows cast by small apertures when using a plane source of monochromatic light as a light source. When you first start up the applet, a circular aperture is used, which is the pattern generated when a plane source of monochromatic light is shined on a small circular hole (about 5 mm across) in an otherwise opaque object.
One thing to note is that the red line represents the outline of the geometrical shadow, which is the shadow that would be cast if there were no diffraction. You can also select a different aperture shape (such as a half-plane, double-slit, triple-slit, rectangle, etc.) from the Aperture popup. Alternatively, you can change the size of the circle by dragging the red line with the mouse.
Overall, if you're looking for a physics simulation software that can help you generate Fresnel diffraction patterns, then Fresnel Diffraction is definitely a software to consider. It's free, Java-based, and provides a user-friendly interface that's easy to use.