Star Patterns

Two pebbles dropped into a still pond produce waves that interfere with each other to form new patterns. Light also has a wave nature. Therefore, light from a distant source shining through the holes of a window screen produces an interference pattern which is similar to what would be seen if you could drop many pebbles simultaneously in a regular pattern on a pond. The shape of the pattern depends on the shape of the screen; for example, a distant source observed through the rectangular weave of a common window screen produces a wave pattern in the form of a rectangular cross, which can be seen easily with the naked eye. Sunlight is made up of many different colours, each of which has a different wavelength. Therefore such light will produce a multi-coloured terference pattern.

This photo was taken through the screen window of a cottage. The rippling surface of a lake has produced a multitude of images of the sun, with each image resulting in a separate interference pattern. The images can be enlarged enough to see the colours clearly by using binoculars, or with a telescopic lens as used here.

Alan Slavin
Trent University
Category 2 (Open) 1st prize

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