Humans detect different wavelengths of light through a sensory system called vision, specifically through the eyes and the specialized cells within them. Color perception is closely related to the detection of different wavelengths of light. Here's an overview of the process:
The eye and its components: The human eye consists of several components involved in the detection and perception of light. The main components include the cornea, iris, lens, and retina. Light enters the eye through the cornea and passes through the pupil, which is controlled by the iris to regulate the amount of light entering the eye. The lens focuses the incoming light onto the retina at the back of the eye.
Retina and photoreceptor cells: The retina is a thin layer of tissue at the back of the eye that contains millions of specialized cells called photoreceptors. There are two types of photoreceptors: rods and cones. Rods are more sensitive to dim light and are responsible for black-and-white vision and peripheral vision. Cones are responsible for color vision and work best in bright light conditions.
Wavelength detection by cones: The cones in the retina are particularly important for detecting different wavelengths of light and contributing to color perception. There are three types of cones, each specialized in responding to different ranges of wavelengths: short-wavelength cones (S-cones), medium-wavelength cones (M-cones), and long-wavelength cones (L-cones). These cones are also commonly referred to as blue, green, and red cones, respectively, based on their sensitivity to different portions of the visible light spectrum.
Photopigments and color perception: Within the cones, there are specific photopigments that absorb light at different wavelengths. The photopigment in S-cones is most sensitive to shorter wavelengths (blue-violet), the one in M-cones is sensitive to medium wavelengths (green), and the photopigment in L-cones is sensitive to longer wavelengths (red). When light of a particular wavelength enters the eye and interacts with the corresponding photopigment, it triggers a chemical reaction that generates electrical signals in the cones.
Neural processing: The electrical signals generated by the cones are transmitted to the brain via the optic nerve. In the visual cortex of the brain, the information is further processed to perceive and interpret different colors based on the patterns of neural activity. The brain combines the signals from the different types of cones and their relative intensities to determine the perception of specific colors.
Overall, the detection of different wavelengths of light by cones and the subsequent neural processing in the brain enable humans to perceive a range of colors. The specific combination of activation across the different cone types and their responses to various wavelengths of light determines the perception of colors across the visible spectrum.