Eye And Color
The eye form a “optical image” on the light sensitive cell of the retina. It is very often compared to a camera in it so workings. However it is like a camera in its focusing properties but is very different after the light has hit the retina. The camera just prints a point to point representation of the image on film, where as the is much more complex and interesting. The visible light is only a very small portion of the electromagnetic spectrum and various wavelength in this visible spectrum of light represent different colors. Short wavelength light is reddish, medium wavelength light is greenish and long wavelength light is bluish. This make apparent in the a schematic of electromagnetic radiation below. The various structures of the eye refract the light entering the eye to focus is on the photosensitive retina. This structure are like the lenses we studied in class.
Path The light takes
* Cornea - The transparent tissue (part of the sclera) towards the front of the eye. Nearly a spherical and accounts for 43 of 59 of the dioptric power of the eye. Light must pass through the cornea to enter the interior of the eye. Imperfection in the spherical shape of the eye, astigmatism, result in vision problems.
* Pupil- opening to the interior of the eye is controlled by the iris. Iris is the thing pigmented smooth muscle part of the choroid. Pupil controls the amount of light entering the eye by dilating or constricting. The diameter of the pupil can range from 2mm to 8mm.
* Aqueous Humor- The liquid between the cornea and lens that has a refractive index (1.336) very close to water.
* Lens-flexible tissue suspended from colliery muscles which can be used for accommodation. Accommodation is the ability to adjust the lens so that both near and far objects can be seen. When the ciliary's muscles are relaxed the lens is relatively flatter and can focus on far object, the opposite applies when the muscles contract. The of dioptric power of the relaxed lens is 19 and can be increased significantly by accommodation. The rim of the lens is irregular and exhibits diffraction so only used when absolutely necessary. The lens has a refractive index of 1.406 at the centre and 1.386 at the rim. The optical axis defined to be a line through the middle of the eye
* Vitreous Humor- liquid between the lens and the retina has a refractive index of 1.337.
* Retina-is the light sensitive part of the eye. The part that converts the light stimuli into neural signals to be interpreted by the cerebral cortex. I will not discuss how the photoreceptors convert the light stimuli into electrical signals, since it involves bio-chemistry, a good description can be found in any physiology book. Light must pass through the neural layers of the retina before reaching the photosensitive layer which consists of rods and cones. The neural layer consist of ganglion cells and bipolar cells. The bipolar...