The Eye
Build confidence in The Eye for GCSE Biology with this free worksheet and full mark scheme — Foundation and Higher exam-style questions with worked answers for AQA, Edexcel and OCR. A separate (triple) biology topic covering accommodation, the pupil reflex, and how long- and short-sightedness are corrected.
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These worksheets and mark schemes are original, written for Virtus Academy and checked against the current AQA, Edexcel and OCR specifications. Every worksheet comes with a full mark scheme.
Topic overview
The eye is a sense organ containing receptors sensitive to light intensity and colour. This is a Triple-only topic.
Light enters through the transparent cornea, which does most of the focusing. The iris controls how much light enters by changing the size of the pupil. The lens fine-focuses light onto the retina, where receptor cells convert it into electrical impulses carried by the optic nerve to the brain.
Accommodation is the process of changing the lens shape to focus on near or distant objects. For a near object the ciliary muscles contract, the suspensory ligaments loosen, and the lens becomes thicker and more strongly curved. For a distant object the reverse happens.
Revision notes
Structures and functions
Cornea: transparent front of the eye that refracts light. Iris: controls pupil size and therefore how much light enters.
Lens: focuses light onto the retina. Retina: contains light receptors. Optic nerve: carries impulses to the brain. Sclera: the tough white outer layer protecting the eye.
Accommodation for a near object
The ciliary muscles contract, which loosens the suspensory ligaments.
The lens then becomes thicker and refracts light rays more strongly. Remembering that contract goes with thicker is the key to this topic.
Accommodation for a distant object
The ciliary muscles relax, which pulls the suspensory ligaments tight.
The lens is pulled thin and refracts light rays only slightly. Myopia is short-sightedness and hyperopia is long-sightedness; both are corrected with spectacle lenses, and also by contact lenses, laser surgery or a replacement lens.
Key points
- The cornea refracts light entering the eye.
- The iris controls the size of the pupil.
- The retina contains light receptors.
- For a near object, ciliary muscles contract and the lens thickens.
- For a distant object, ciliary muscles relax and the lens is pulled thin.
- Myopia is short sight; hyperopia is long sight.
Worked examples
Example 1
Describe how the eye focuses on a near object. [3 marks]
Model answer
The ciliary muscles contract (1 mark), which loosens the suspensory ligaments (1 mark). The lens then becomes thicker and refracts the light rays more strongly (1 mark).
Example 2
Explain how the eye responds to bright light. [3 marks]
Model answer
Light receptors detect the increased light intensity (1 mark). The circular muscles of the iris contract and the radial muscles relax (1 mark), making the pupil smaller so less light enters the eye and the retina is protected from damage (1 mark).
Example 3
Name the structure that carries impulses from the eye to the brain. [1 mark]
Model answer
The optic nerve (1 mark).
Common mistakes
Saying the lens does most of the focusing.
The cornea does most of it; the lens fine-focuses.
Getting accommodation backwards.
Ciliary muscles CONTRACT for a NEAR object, making the lens thicker.
Confusing the iris with the pupil.
The iris is the muscular ring; the pupil is the hole it controls.
Saying the pupil contracts.
The iris muscles contract; the pupil simply gets smaller.
Exam tips
- Learn accommodation as contract-loosen-thicker for near objects.
- Name the cornea as the main refracting structure.
- Distinguish the iris from the pupil carefully.
- Remember this is a Triple-only topic.
Key terms
- Cornea
- The transparent front of the eye that refracts light.
- Accommodation
- Changing the lens shape to focus on near or distant objects.
- Ciliary muscle
- The muscle that changes the shape of the lens.
- Retina
- The light-sensitive layer at the back of the eye.
Related topics
Written and reviewed against the current AQA, Edexcel and OCR specifications. Spotted an error? Let us know.