Color of Water
Without a human eye and brain there is no color!
Bryce Johnson, Lori Lambertson, Anna McGaraghan, Paul Doherty
This workshop is available on the website : http://www.exo.net/~pauld/
The plan
Discussion question in small groups: 1. What causes the color of water? 2. Pick a color on the chart and guess why the water might be that color.
Look at the color of tap water in a long tube.
Exhibit: Colored Shadows, to show color subtraction (PD)
Make turbidity tubes, calibrate them using different dilutions of TSS. Graph data. (LL, BJ)
Make hinged mirrors.
Walk to St. Francis pier:
turbidity tubes (BJ, LL)
hinged mirrors (BJ, PD)
color charts (BJ, AM)
Phytoplankton and water color (AM)
Color dilution (BJ, LL)
Lee filter demonstration (PD)
Reflection, absorption, scattering (PD)
Exhibits
Colored shadows Combine light from red, green and blue bulbs to make white light, then use shadows to subtract colors.
Disagreeing about color http://www.exo.net/~pauld/CILS/CILScomparingyellows.html, This exhibit answers the question "Do other people see the same colors I see?"
Mix and Match http://www.exploratorium.edu/exhibits/mix_n_match/ How many colors can you see?
Snacks
CD Spectrometer Make your own spectrometer with a compact disk.
Serial Dilution and Phytoplankton
Articles and Websites
Red and Black tides, pdf
Ocean Data Center http://oceandatacenter.ucsc.edu/home/oceandatacenter.html
Ocean Color Web http://oceancolor.gsfc.nasa.gov
Graphs
Colors of Water
Turbidity tube calibration
Reflectance of Water versus angle
Lower curve is light polarized perpendicular to the water surface, upper curve is light polarized parallel.
Red Tide (Wikimedia commons)
Images from the article Red and black tides
Color of the sea versus biomass in mg/m^3
Absorption spectrum of water
source http://www.lsbu.ac.uk/water/vibrat.html#blue
The Absoption Coefficient, a m^-1 of pure water in the visible part of the spectrum.
I = I0 e^(-ax)
Absorption spectrum of chlorophyll
The sensitivities of the human cones
The CIE Color Chromaticity Diagram 1931
The official names for colors. The spectrum is wrapped around the upper boundary with wavelengths in micrometers.
If you mix two wavelengths of light, draw a line between the wavelengths, move along the line to mix colors
and see the resulting color.
