Displaying Invisible Light: False Color
What would the world look like if you could see light that is currently invisible to us – say infrared, ultraviolet or microwaves? What color would we interpret them as? Remember all electromagnetic energy is colorless—we see color because of functions going on in the eyes and brain.
Some animals can sense energies of light (electromagnetic energies) that are invisible to humans. Bees sense ultraviolet reflected from flowers, crucial to discriminating types of flowers for pollination. Butterflies see from the UV to red, with the added ability to see polarized light. Snakes sense thermal infrared, which they rely upon to locate their prey. These powers of seeing energies invisible to the human eye are critical to their survival. Then there is Superman with his X-ray vision, but that’s another story...
Man-made satellites have sensors that detect energies that are invisible to our eyes, and we use clever ways to display such energies on computers. With the earliest satellites, only one band of electromagnetic information could be visualized at one time by using gray shades. With the development of color display monitors (originally television screens), three sets of measurements could be displayed at once by placing each set of information in one of the primary colors of the display. This technique requires the viewer to understand how colors are created on a computer display monitor. Colors visible on the computer display are based on the overlap of the three satellite detector intensities, which depend on the physical properties of the system object being observed. With satellite sensor data, it’s possible to display images Earth’s surface, gas components of the atmosphere, the Earth’s magnetic field, etc.
Materials
Download the FalseColor software see a brief tutorial.
MtStHelens_1973.jpg (download image on lower right).
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