How do the eyes detect light and colour?

The eyes detect light and colour through photoreceptor cells in the retina called rods and cones.

The human eye is a complex organ that allows us to perceive the world around us in vivid detail and colour. This is made possible by the presence of photoreceptor cells in the retina, which is the light-sensitive layer at the back of the eye. These photoreceptor cells are of two types: rods and cones.

Rods are responsible for detecting light and dark changes, shape and movement and provide us with night vision. They are more sensitive to light and allow us to see in low light conditions. However, they do not perceive colour and detail. This is why our vision is less colourful in dim light.

On the other hand, cones are responsible for colour vision and work best in relatively bright light. Humans typically have three types of cones that are sensitive to short-wavelength (blue), middle-wavelength (green), and long-wavelength (red) light. The brain combines the information from these different types of cones to give us our perception of colour.

When light enters the eye, it strikes the photoreceptor cells in the retina. This light energy triggers a chemical reaction in the cells. In rods, the light causes a pigment called rhodopsin to break down into opsin and retinal. This reaction sends an electrical signal to the brain, which interprets it as an image. In cones, the process is similar but involves different pigments (photopsins) that are sensitive to different wavelengths of light.

In summary, the detection of light and colour by the human eye is a complex process involving the interaction of light with photoreceptor cells in the retina. The rods and cones in the retina respond to different aspects of light, with rods being more sensitive to light and dark changes, and cones providing colour vision. The brain then interprets these signals to create the images we see.