Optics - the human eye and coomon defects

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Physics In Action               Eye Defects                        Gurmeet Sidhu

Eye Defects

Vision:-

The mammalian eye could be regarded as a miracle of evolution. In order to produce an image the eye has to act as an Optical refracting System (to focus a sharp image) and a Photo Detector (to analyse the image and send information to the brain). At the front of the eye is the optical system, made up of the transparent curved Cornea and the adjustable biconvex Lens. The photo detector is the layer of light-sensitive cells at the back of the eye, called the Retina. The amount of light entering the eye is controlled by the Iris. Sharp focusing is achieved by altering the shape of the lens. The shape of the lens is controlled by the ring of ciliary muscle which runs round the outside of the lens.

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Defects in the eye:-

  1. Long Sight (Hypermetropia)

In this condition we can see distant objects more clearly that ones that are nearby. This is usually because the cornea is not curved enough, which reduces the angle of refraction, and the lens cannot accommodate sufficiently to bring the diverging rays from near objects into sharp focus on the retina.

  1. Short Sight (Myopia)

In this condition near objects are clearly seen, but distant objects cannot be brought into the focus. It happens when the cornea is too curved; the light from distant objects is ...

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Picture references are just placed anywhere in the main body of text and this looks untidy. Parts of the eye are given capital letters which they shouldn't have. Other punctuation, grammar and spelling looks okay. Some spaces occur in words due to the pdf file.

The biology is explained clearly, and the images outline the functions of the eye and possible defects. The different types of common defects are explained, but refraction should be defined before the candidate discusses problems with the eye to aid clarity. Pictures are used in a good way to explain the defects and how they can be corrected. The candidate should discuss how the lenses work exactly in the text but this is aided well by the images. I'm not sure why the eye formulas are included.

Response to the question is done well. The candidate outlines a few common defects after explaining a bit about the biology of the eye and then explains how these can be corrected and some of the risks associated. The sections are clearly set out. This piece is done to a high level.