NetLogo User Community Models

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Download If clicking does not initiate a download, try right clicking or control clicking and choosing "Save" or "Download".(The run link is disabled for this model because it was made in a version prior to NetLogo 6.0, which NetLogo Web requires.)

WHAT IS IT?

This model looks at the absorption of light by colored filters. In this case the filter is a chamber filled with gas molecules that absorb specific wavelengths of light.

HOW IT WORKS

Turtles representing photons are created and directed at a surface. Initially they are a random mixture of red, green, and blue, using the RGB system. When they hit the surface, you can choose which ones are absorbed. All the others pass through the filter.

The circle to the right displays the color of the average RGB values of all the photons that make it through the filter.

HOW TO USE IT

Setup and run the model. Try absorbing different colors. Try absorbing everything. Does the filtered color match your expectations?
To observe more closely what is going on, slow down the model with the slider above the graphics window. Depending on the settings, what happens to each incoming color when it interacts with a gas molecule?

THINGS TO NOTICE

THINGS TO TRY

EXTENDING THE MODEL

This model deals with only three colors and their mixtures. Try refining the model to deal with a larger range of colors and absorptions.

NETLOGO FEATURES

This model makes use of the "rgb R G B" primitive, which converts an RGB value (each number ranging from 0 to 1) to a NetLogo color. For instance, the color red is
"rgb 1 0 0". The color blue-green is "rgb 0 1 1".

If the gas absorbs red, it changes the first number to 0. That is, RGB 1 0 0 becomes RGB 0 0 0, which is black. Knowing these rules, can you figure out what absorption does to each color?

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CREDITS AND REFERENCES

This model was created by Ed Hazzard at the Concord Consortium as part of an activity for an NSF-funded project called ITSI (Information Technology in Science Instruction). See http://itsi.concord.org.