To help overcome the problem of uncertainty and guessing in subjects, signal detection psychology theory approaches the subject's behavior in detecting a threshold as a form of decision making. The stimuli that affect vision are light waves psychology, a type of electromagnetic wave energy. The human eye is capable of responding to electromagnetic energy with a wavelength of between 380 and 760 nanometers. Wave amplitude is the height of the wave. It primarily determines our experience of brightness psychology.
Light rays enter the eye through the cornea, the outer membrane that covers the eyeball.
The light rays are focused by the lens psychology, which flattens out for more distant objects and thickens for those closer. The focused images fall on the retina psychology, a patch of tissue at the back of the eyeball. In the retina, the rods psychology respond to differences in brightness, and are most important for seeing in dim light. They are most sensitive to light waves in the 500 nm range, or to blue and green light. The cones psychology respond to hue, or color variations, and are most important for color vision in bright light.