Experiment:
Afterimages

When looking at the white and black rasters small grey points appear where the lines intersect. In our example, the points on the left-hand side appear lighter than those on the right-hand side. If you continue to observe the 2 images, the whole raster is full of points.

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Further material for this article.

Experiment: Afterimages

When looking at the white and black rasters small grey points appear where the lines intersect. In our example, the points on the left-hand side appear lighter than those on the right-hand side. If you continue to observe the 2 images, the whole raster is full of points. Try it for yourself. You will be surprised!


Stare at the intersections and blink a little. Soon both the images are full of grey points.

You can try this experiment with your pupils. Download the templates and paint them accordingly.

Painting instructions

The squares on the left marked X should be painted black. The squares on the right are left open but the grid lines marked X should be painted in black.

How is this possible?

Afterimages occur mainly when a strong colour impression is made on a neutral surface. This phenomenon can be experiences when shutting your eyes after observing a strong source of light. In our example, just by looking at the black and white rasters, interesting afterimages caused by the strong colour contrast occur. These light and dark points illustrate the ability of our eyes to protect themselves against light sources, which are too strong.