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'White Box' printed from http://nrich.maths.org/
The White Box contains a number of filled triangles.
Your challenge is to find the locations of those filled triangles in the grid.
You can fire rays into The White Box and observe where the rays exit using the Experiment Window.
Some rays will pass straight through the Box but some will be deflected by the filled triangles.
You can use the Hypothesis Window to test your ideas. Clicking on a triangle once marks the triangle as empty, clicking again fills it.
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NOTES AND BACKGROUND
Anyone attempting to understand anything about the nature of atoms and molecules has to try to come to terms with their almost inconceivably tiny nature. A single hair is about the same width as a million atoms; a glass of water contains about 10 000 000 000 000 000 000 000 000 molecules. The minute size means that they're beyond the range of even the most powerful microscope, so to gain
understanding about the ways atoms are arranged within crystals and molecules, scientists need to use indirect methods.
One method involves firing rays of sufficient energy to break bits off the molecules. These particles will of course be smaller still, but they may be easier to recognise. The experimenter can then use the pieces like a jigsaw to explore how they fitted together in the original molecule.
A less destructive process involves not breaking up the structure, but deducing its arrangement by observing the areas where rays fired into it emerge. Some rays pass straight through, while others are deflected by atoms within the structure. The White Box interactivity models this process and makes an intriguing challenge as well.