B4.5.2.3

The eye (biology only)

Content

Students should be able to relate the structures of the eye to their functions. This includes:

  • accommodation to focus on near or distant objects
  • adaptation to dim light.
  • The eye is a sense organ containing receptors sensitive to light intensity and colour.



Students should be able to identify the following structures on a diagram of the eye and explain how their structure is related to their function:

  • retina
  • optic nerve
  • sclera
  • cornea
  • iris
  • ciliary muscles
  • suspensory ligaments.
  • Accommodation is the process of changing the shape of the lens to focus on near or distant objects.

To focus on a near object:

  • the ciliary muscles contract
  • the suspensory ligaments loosen
  • the lens is then thicker and refracts light rays strongly.

To focus on a distant object:

  • the ciliary muscles relax
  • the suspensory ligaments are pulled tight
  • the lens is then pulled thin and only slightly refracts light rays.
  • Two common defects of the eyes are myopia (short sightedness) and hyperopia (long sightedness) in which rays of light do not focus on the retina.
  • Generally these defects are treated with spectacle lenses which refract the light rays so that they do focus on the retina.
  • New technologies now include hard and soft contact lenses, laser surgery to change the shape of the cornea and a replacement lens in the eye.
  • Students should be able to interpret ray diagrams, showing these two common defects of the eye and demonstrate how spectacle lenses correct them.

Recognise/draw/interpret diagrams. Translate from data to a representation with a model. Use models in explanations, or match features of a model to the data from experiments or observations that the model describes or explains. Make predictions or calculate quantities based on the model or show its limitations. Give examples of ways in which a model can be tested by observation or experiment.,

Describe and explain specified examples of the technological applications of science. Describe and evaluate, with the help of data, methods that can be used to tackle problems caused by human impacts on the environment.