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.
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.
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.