How do we see? Most people would just say that we see with our eyes and this is true but it is also more complicated than that. In some ways the eye is a bit like a camera that sends images to our brain but it is very sensitive and can be easily damaged. The eye itself is a very compact and complex apparatus. The eye is only around 25 mm wide and deep and slightly less in height.
A complex set of 6 muscles (known as the extra ocular muscles) attached to the outside of the eye help it to move in any direction. The exterior of the eye has a tough layer called the sclera. This wraps almost around the whole eye except for one sixth at the front that is clear and this is called the cornea. Just underneath the sclera is the choroids layer, which contains blood vessels for the eye.
The cornea is multi-layered. The outer layer is able to replace damaged cells rapidly, the inner layers are rigid and provide a barrier against infection. The cornea is the main cause of refraction of the image that we finally see. So how do all of these complex parts work together to help us see? At the front of the sclera is a transparent window called the cornea. All light must first pass through the cornea and then through a hole called the pupil. This is the black spot at the front of the eye.
The pupil can change size to allow different amounts of light through. When it is dark the pupil opens up very wide and when it is bright, the pupil closes up and only allows a small amount of light to go through. The muscle that controls the pupil is called the iris. This is the coloured circle that you see when you look at someone’s eyes. Once the light has passed through the pupil it enters the lens. The lens is about the size of a pea and it is behind the iris.
The Essay on Polarized light lab report
ABSTRACT Ordinary light such as that from a light bulb is a form of wave motion that consists of electrical and magnetic fields that vibrate at right angles to the direction of travel of a light beam. Light waves that vibrate in a single plane are called polarized light waves. Such waves can be produced by passing light through polarizing filters. The experiment conducted was composed of crossed ...
It is clear and rubbery and can change shape. As the light enters the lens it changes shape so it can focus the light rays onto the back of the eye to form a picture. The picture it forms is perfectly clear but upside down and back to front. The back of the eye is called the retina and it contains sensitive cells, which convert the light to electrical impulses, which are sent to the brain along the optic nerve. The brain then decodes these messages and turns the picture the right way up. All of the parts of the eye must be working correctly for the image to be formed properly.
When something is wrong with one part of the eye the picture will not be correct. If the eyeball is too short the image may be formed behind the retina. This is called long sight. This means that people can see things clearly that are far away but nearer objects will be blurry. If the eyeball is too long the image can be formed in front of the retina. This is called short sight.
This means that people can see nearby objects clearly but anything further away will be blurry. Both of these problems can be helped with glasses or contact lenses as these help to change the path of the light rays so that they are correctly focused on the retina. If the optic nerve is damaged it may distort the impulses that are sent to the brain and this can result in blindness. It is important to look after your eyes, as sight is one of our senses that we rely on the most.
