Final answer:
The difference in spectral sensitivity in cones is caused by specific molecules called opsins that are sensitive to different wavelengths of light. There are three types of cone opsins in humans, each sensitive to a specific primary color: red, green, and blue. By comparing the activity of these three different cones, the brain can extract color information from visual stimuli.
Step-by-step explanation:
Cones are photoreceptor cells in the eye that are responsible for color vision. The difference in spectral sensitivity in the cones is caused by the presence of specific molecules called opsins. There are three types of cone opsins in humans, each sensitive to a specific wavelength of light: red, green, and blue. These opsins allow cones to perceive different colors by comparing the activity of the three different cones. For example, a bright blue light that has a wavelength of approximately 450 nm would activate the 'red' cones minimally, the 'green' cones marginally, and the 'blue' cones predominantly. The brain then calculates the relative activation of the three different cones and perceives the color as blue. In contrast, rods, another type of photoreceptor cell, are more sensitive to low-intensity light and do not sense color. Therefore, our low-light vision is primarily in grayscale.