ion is regarded as the dominant concept of human beings and while we can live without it and not be deceived, what you learn is NOT a deception. When we talked about your sense of hearing Meanwhile, what is red may appear dim and muted when the wave travels at low amplitude, but it is much brighter if the wave has high amplitude as well as high power. But the visible light we see is just a small fraction of the full electromagnetic wavelength, ranging from short gamma rays to long wavelengths. Just as mechanoreceptors in the ear or speech chemoreceptors convert sounds and chemicals into action, so your photoreceptors of your eyes convert light energy into sensory nerves that the brain cannot understand. To find out how all of this works, let us first consider the anatomy of the eyes. Some of the first things you will see near your middle eyes are all the external resources - such as eyebrows that help keep you from sweating if you forget your head on racquetball, and the most sensitive eyebrows that cause visible blinking, like a sandy beach. These features, along with eyelids and tear-gasping kits, are available to help protect your delicate eyes.
The eyeball itself is not an unusual circle, measuring about two inches [2.5 cm] in diameter. It is completely empty - it is full of fluids that help it maintain its shape - and you can only see the front half of the entire ball. Some of it is packed in a protective oil pack, strapped down with six straps like the muscles of the outer eye, and tightened to the skeletal muscle of your skull. Although all of these gears usually do an excellent job of keeping your eyeballs inside your head (good), in very rare cases, perhaps after a head injury or - or even a really serious sneeze! - those suckers can come out straight - a condition called globe luxation, which you don't really want to google. I'll stay here while you're Google. Now, you do not need to pull out an eyeball to learn how it is made. I will keep you in trouble and tell you that its wall is made up of three different layers - fibrous, vascular, and inner layer. The outer fibrous layer is made up of connective tissue. Most of them are white matter called sclera, and the most prominent part is the exposed cornea. The cornea is like a window that lets light into the eye, and if you have ever felt the excruciating pain of a scratched eye, you know how bad it is to damage something loaded with pain receptors. Go down a little deeper, the lining of the arteries in the middle of the wall contains the posterior choroid, the membrane that supplies all the layers with blood.
Previously, there was also a ciliary body, a ring of muscle tissue around the lens; but the most famous part of this central layer is the iris. The iris is that part of the eye with a different color of your own. It is made of smooth muscle, shaped like a donut, and separated between the cornea and the lens. Those sphincter muscles - yes, of course, you have sphincters everywhere! - contract and expand, changing the size of your student's black dot. The reader himself simply opens it to let the light penetrate the eye. You can see how the iris protects the eye from too much light when you light a torch in your friend's eye in a dark room. Their students will move from open to skilled in a matter of seconds. Light enters the cornea and pupil and strikes the lens - a convex, a light disk that absorbs that light and absorbs it into the retina, forming the inner layer of the back of the eye. Your retinas are loaded with millions of photoreceptors that do a vital job of converting light energy into electrical signals that your brain will detect. These reception cells come in two forms - rods and cones - which I will return to in a minute. But the retina itself has two layers, an outer layer of color that helps absorb light so that it does not scatter near the eyeball, and
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