The page explains Kepler's ideas and because it shows rather than tells, it also illustrates the key part which applets are set to play in physics education. Walter Fendt's materials are also reproduced around the world. His own Web site, Java Applets on Physics , provides resources on, for example, electrodynamics, the theory of relativity and nuclear physics. One of the wide range of applets illustrates the refraction of light. A ray of light is incidenting from the top left of the illustration to the boundary surface of two media.
Students can select and change the substances and vary the incidenting ray of light.
By using the application, they can also see the angles of reflection and refraction change as they do so. Diffraction is a phenomenon which involves the bending of waves around obstacles and Sergey Kiselev and Tanya Yanovsky-Kiselev have designed an applet which shows the simplest case of diffraction, single slit diffraction. Students can change the colour of the light and the width of the slit simply by dragging the mouse of their computer. By creating java applets, Hwang, Fendt and the Kiselevs illustrate and demonstrate and insist that students get involved. Their aim is also to make resources more interactive but they've chosen to use Shockwave, a Web browser plug-in, rather than to create java applets.