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The human eye is a complex sensory organ that is designed to see light and color, which play an important part in the visual communication process. While there is currently a lot that we do understand about this process, our knowledge is still very incomplete, and there's plenty of research ongoing.
Above is an image of the side of the eye. The retina is a thin, transparent tissue at the back of the eye that contains light-sensitive receptors called the rods and cones.
Rods are the long, thin, light-sensitive parts of the retina that process night vision. Cones are the light-sensitive parts of the retina that process color and day vision. In the retina, there are as many as 120 million rods and 6 or 7 million cones.
When you see an image, light passes through the eye lens and hits the retina. In the retina, those rods and cones create nerve impulses and convert light into electrical signals, which travel through the brain via the optic nerve.
The optic nerve is the tissue that connects the retina to the visual cortex in the back of the brain, which you can see in the image below.
If you look at the side cut of a face below, you can see the image of the eye from earlier, as well as a nice view of the brain.
Light hits the retina with your cones and rods, and that information travels through the optic nerve, which routes it to the lateral geniculate nucleus. The lateral geniculate nucleus then routes the information to the lower back side of the brain called the visual cortex. This is the part of the brain which processes visual information from the retina, communicated via a network of nerve cells.
As you can see, there is a lot of complexity to the way we process images and light. Electromagnetic radiation is another name for light, and the human eye is only sensitive to the portion of it known as visible light. All electromagnetic radiation, or light, travels in waves at the same speed, which we refer to as the speed of light.
When we talk about light traveling in waves, we also talk about frequency, which is the number of waves passing a certain point per second, measured in hertz. Light can be characterized by its wavelength.
EXAMPLE
The human eye can see wavelengths somewhere between 400 and 900 nanometers, which is referred to as visible light within the electromagnetic spectrum. Light waves with a shorter wavelength and a higher frequency, such as gamma rays, x-rays, and ultraviolet light, are beyond the human eye's visibility range. Infrared light, microwaves, and radio waves are also beyond what the human eye can see, due to their longer wavelengths and lower frequencies.
Source: THIS WORK IS ADAPTED FROM SOPHIA AUTHOR MARIO E. HERNANDEZ
