Edexcel GCSE Biology 1BI0
Key Concepts in Biology
Cells and Control
Genetics
Natural Selection and Genetic Modification
Health, Disease and the Development of Medicines
Plant Structures and Their Functions
Animal Coordination, Control and Homeostasis
Exchange and Transport in Animals
Ecosystems and Material Cycles
Cells and Control
Eye defects and how they are corrected
- 3 things to know
- Paper 1
Overview
Cataracts and their replacement with an artificial lens, the causes of short- and long-sightedness and their correction with concave and convex lenses, contact lenses and laser surgery, and colour blindness, its cause in cone cells and why glasses cannot correct it.
What you need to know
Answer each one before you reveal it.
Explain how a cataract affects a person's sight.
What is short-sightedness?
Questions from this subtopic
Each one with the model answer underneath.
- 1
What is a cataract?
Model answer
A cloudy patch that develops in the lens of the eye.
- 2
Explain how a cataract affects a person's sight.
Model answer
Less light reaches the retina, so vision becomes blurred and misty and colours look less vivid.
- 3
What is short-sightedness?
Model answer
A defect in which distant objects look blurred because their image is brought to a focus in front of the retina.
- 4
What causes short-sightedness?
Model answer
The eyeball is too long, or the lens is too curved and refracts the light too strongly.
- 5
What is long-sightedness?
Model answer
A defect in which near objects look blurred because their image would come to a focus behind the retina.
- 6
What causes long-sightedness?
Model answer
The eyeball is too short, or the lens is too thin or stiff to refract the light strongly enough.
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