S12.3.3

Knows that only a narrow range of wavelengths of electromagnetic radiation can be seen by the human eye; differences of wavelength within that range of visible light are perceived as differences in color.

The Shadow of the Dog

The dogs I know like to be walked at least twice a day -- once in the morning, and once in the evening. But even though I'm the same person and it's the same dog in the morning and evening, our shadows change... In the morning, our shadows point in one direction. This is true regardless of which way we are facing. The shadows of trees, buildings, cars, fire hydrants, and blades of grass all point in the same direction as ours. In the evening, our shadows all point in approximately the opposite direction.

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Color and Spectrum

Human beings' color vision allows us to distinguish both large and subtle differences between objects of similar color. Consider a forest, with its multitude of greens. But objects with similar colors are not necessarily the same, as the jade and seaweed found on some Pacific coast beaches illustrate. Researchers, chemists, criminalists, and many other investigators study and compare objects and learn about their compositions by breaking the light down into its composite colors, a technique called spectroscopy

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