The Eye
THE EYE.
The normal sighted human eye perceives an object which is ‘described’ by light rays and how they are bent by it . Usually, the image of the object is picked up on the retina, on the area of the Central Forea as an upside down picture which is then ‘righted’ by the brain in order that the object may be seen.
Different distanced objects are perceived by the eye and the lens is the part that makes this possible.
Objects which are close to the eye are seen by the eyes’s lens becoming thicker and more bulbous in order to create a lens with a higher refractive index for detailed sight, i.e. for close work like sewing . The CILIARY MUSCLE contracts, pulling the Ciliary process and Choroid towards the lens. Tension is therefore released ob both the SUSPENSORY LIGAMENTS and the lens and this makes the lens able to focus the light rays successfully on the retina.
Figure 1. Focussing on a close object.
http://www.sciencelearn.org.nz –
In Distance sight, the CILIARY MUSCLE now relaxes and the lens stretched tight in all directions. This makes it taller/thinner and therefore better able to refract the light at an angle which will result in the image being focussed on the retina.
Figure 2. Distant object Focus.
http://hyperphysics.phy-astr.gsu.edu/hbase/vision/accom.html
DEFECTS OF VISION.
MYOPIA
Ray diagram of myopic eye.
http://www.meritnation.com/discuss/question/3529249/0/draw-a-ray-diagram-of-myopic-eye-and-its-rectification
Myopia is caused by either a flattened eyeball or a ‘thick lens’, i.e. thicker than a normal sighted lens. In both cases this means that the image focusses short of the retina and results in blurred vision.
Ray diagram of rectification of myopic eye http://www.meritnation.com/discuss/question/3529249/0/draw-a-ray-diagram-of-myopic-eye-and-its-rectification The addition of a concave lens enables the light rays to be bent twice, once by the external lens and secondly, by the eye’s
The normal sighted human eye perceives an object which is ‘described’ by light rays and how they are bent by it . Usually, the image of the object is picked up on the retina, on the area of the Central Forea as an upside down picture which is then ‘righted’ by the brain in order that the object may be seen.
Different distanced objects are perceived by the eye and the lens is the part that makes this possible.
Objects which are close to the eye are seen by the eyes’s lens becoming thicker and more bulbous in order to create a lens with a higher refractive index for detailed sight, i.e. for close work like sewing . The CILIARY MUSCLE contracts, pulling the Ciliary process and Choroid towards the lens. Tension is therefore released ob both the SUSPENSORY LIGAMENTS and the lens and this makes the lens able to focus the light rays successfully on the retina.
Figure 1. Focussing on a close object.
http://www.sciencelearn.org.nz –
In Distance sight, the CILIARY MUSCLE now relaxes and the lens stretched tight in all directions. This makes it taller/thinner and therefore better able to refract the light at an angle which will result in the image being focussed on the retina.
Figure 2. Distant object Focus.
http://hyperphysics.phy-astr.gsu.edu/hbase/vision/accom.html
DEFECTS OF VISION.
MYOPIA
Ray diagram of myopic eye.
http://www.meritnation.com/discuss/question/3529249/0/draw-a-ray-diagram-of-myopic-eye-and-its-rectification
Myopia is caused by either a flattened eyeball or a ‘thick lens’, i.e. thicker than a normal sighted lens. In both cases this means that the image focusses short of the retina and results in blurred vision.
Ray diagram of rectification of myopic eye http://www.meritnation.com/discuss/question/3529249/0/draw-a-ray-diagram-of-myopic-eye-and-its-rectification The addition of a concave lens enables the light rays to be bent twice, once by the external lens and secondly, by the eye’s