Line chart showing the degree of stimulation of each of the 3 types of cone cells and the rod cells by different wavelengths of light. The <PERSON> axis is wavelengths from 390 nanometers to 750 nanometers. The Y axis is from 0 to 100. The lines for the cones show three bell-shaped curves, peaking at wavelengths 420, 534, and 564. The line for the rods show a bell-shaped curve peaking at 498.