In elementary science we are taught that light always travels in straight lines. But this is not strictly true. Uninterrupted light waves may travel in straight lines through empty space, but if light is partly blocked by a barrier, or passes through a narrow slit, a small hole or some other aperture, then it is diffracted. The light passing beyond the barrier spreads out in new directions, forming a complex pattern of bright and dark bands known as a diffraction pattern. The exact form of the pattern depends both on the wavelength of the light and the size and structure of the aperture or object.

The CD-ROM Multimedia Diffraction is an interactive resource to support the teaching and learning of this important phenomenon. The resource concentrates on optical diffraction effects and applications. Optical analogues of X-ray diffraction effects are also discussed. The CD-ROM presents a library of images of diffraction patterns (recorded photographically) and tools to measure them. For each image, a text file provides a short introduction and some suggestions for student work. Users can measure and record intensities at points in the patterns, plot graphs of the intensity profile across sections in the patterns, and measure the dimensions of the diffracting objects used to produce the patterns.

Sequences are selected from the list box:

Patterns are measured by dragging a wire:

And plotting a graph: