Slide #1.

Y-axis is the proportion of light absorbed by rhodopsin (rods) at each wavelength indicated on the xaxis. Remember that at the retina, light has to be absorbed in order to have an effect. CRUCIAL FACT:A single receptor (rod here, same for cones) is triggered by amount of light energy, which, roughly is the absorption value on the yaxis TIMES the amount of light at the wavelength.
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Slide #2.

Important column. These numbers = proportion x number of photons # Incident Photons 1000 1000 1000 1000 1000 1000 1000 1000 1000 1000 Number of incident photons is an Independent variable # absorbed for # incident # absorbed Proportion Percent 1000 photons for 2000 0.01 1 10 2000 20 0.02 2 20 2000 40 0.03 3 30 2000 60 0.04 4 40 2000 80 0.05 5 50 2000 100 0.06 6 60 2000 120 0.07 7 70 2000 140 0.08 8 80 2000 160 0.09 9 90 2000 180 0.1 10 100 2000 200
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Slide #3.

Simplest light/color matching experiment to illustrate psychological consequences of a single sensitive pigment operating. Standard Variable --- brightness varies, wavelength stays the same. Question for observer: Do the two lights look identical? (Same) or not (Different)? Adjust brightness (amount of light) in variable light. Lighter than before -- can make this lighter or darker. Keep asking if the two lights look identical or not.
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Slide #4.

Use the arrow keys to toggle through a small sample of brightness variations in the variable light. Standard --One fixed wavelength for and experimental trial Variable --Also one wavelength, but a different one from the standard In this kind of matching experiment, one light stays the same and one light changes brightness (amount of light energy). As the brightness of the variable light changes, the wavelength stays the same.
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Slide #5.

Visual pigments In rods and cones
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