AQA GCSE Biology Foundation (8461), Foundation tier · Homeostasis and response › The human nervous system
Practise The eye. 7 exam-style questions on this subtopic, at up to four difficulty levels, with full mark schemes and a progress tracker. Free, no account needed.
The structure of the eye, how it focuses on near and distant objects (accommodation), how it adapts to dim and bright light, and how short and long sight are corrected. Expect labelling, 'explain how the eye focuses' chains and ray diagram questions. This subtopic is in GCSE Biology only.
Key facts
Cornea refracts light; iris controls pupil size; lens focuses light on the retina
Retina = light receptors; optic nerve = impulses to the brain; sclera = tough protective outer layer
Near object: ciliary muscles contract, ligaments slacken, lens thicker, more refraction
Dim light: pupil dilates; bright light: pupil constricts
Myopia (short sight): focus in front of the retina → concave lens
Hyperopia (long sight): focus behind the retina → convex lens
Other treatments: contact lenses, laser surgery on the cornea, replacement lens
Notes
Structures and their functions
diagram
The eye is a sense organ containing receptors sensitive to light intensity and colour.
Cornea: transparent front layer that refracts (bends) light into the eye.
Iris: coloured ring of muscle that controls the size of the pupil (the hole light passes through), and so how much light enters.
Lens: focuses light onto the retina. Its shape is changed by the ciliary muscles and suspensory ligaments.
Retina: contains the light receptor cells. Optic nerve: carries impulses from the retina to the brain.
Sclera: tough white outer layer that protects the eye.
Structure of the eye (light enters from the left).
Accommodation (focusing)
diagram
Accommodation is changing the shape of the lens to focus on near or distant objects.
Near object: ciliary muscles contract → suspensory ligaments loosen → lens becomes thicker → light is refracted more strongly.
Distant object: ciliary muscles relax → suspensory ligaments are pulled tight → lens is pulled thin → light is refracted only slightly.
Accommodation: the lens changes shape so the light is always focused on the retina.
Adapting to light levels
In dim light the pupil widens (dilates) so more light reaches the retina. In bright light it narrows (constricts), protecting the retina. This is a reflex.
Defects of vision
diagram
Myopia (short sight): distant objects look blurred because light focuses in front of the retina (lens too curved or eyeball too long). Corrected with a concave (diverging) lens.
Hyperopia (long sight): near objects look blurred because light focuses behind the retina (lens too flat or eyeball too short). Corrected with a convex (converging) lens.
Defects of vision and their correction (red dot = where the light is focused).
Newer treatments: hard and soft contact lenses, laser surgery to change the shape of the cornea, and a replacement lens inside the eye.
How to answer each type of question
Name a part of the eye or give its function
1 mark eachGrade 4
Give the exact name (e.g. 'suspensory ligaments', not 'strings').
For a function, say what the part does, not where it is.
Example. (a) Name the part of the eye that contains light receptors. (b) Give the function of the optic nerve. (c) Give the function of the iris.
Show the model answerHide the model answer
(a) Retina (1) (b) Carries (nerve) impulses from the retina to the brain (1) (c) Controls the size of the pupil / how much light enters the eye (1)
Don’t lose marks
Saying the suspensory ligaments contract. Only muscles contract; ligaments are pulled tight or go slack.
Getting accommodation the wrong way round: for a near object the muscles contract and the lens gets thicker.
Saying the lens focuses light 'on the pupil' or 'on the optic nerve'. Light is focused on the retina.
Calling the black hole in the middle the iris. That is the pupil; the iris is the coloured muscle around it.
Swapping the lenses: concave corrects short sight, convex corrects long sight.
More tips
Memory tricks
Reading is hard work: the ciliary muscles contract for near objects. Looking into the distance is relaxing: they relax.
Muscles and ligaments do the opposite: muscles contract → ligaments slacken; muscles relax → ligaments tighten.
Short sight: the focus falls short (in front of the retina). Long sight: the focus goes too far (behind the retina).
Myopia needs a 'minus' (concave) lens; hyperopia needs a 'plus' (convex) lens.
Exam technique
Accommodation answers need the chain in order: ciliary muscles → suspensory ligaments → lens shape → refraction. Each link is usually a mark.
Say the lens refracts light 'more' or 'less', and finish with 'so the light is focused on the retina'.
On ray diagrams, draw straight lines with a ruler and add arrows showing the direction of the light.
What each grade needs
What you need to be able to do, from the first marks up to the top grade.
Grade 3
Label the main parts of the eyeCornea, iris, pupil, lens, ciliary muscles, suspensory ligaments, retina, optic nerve and sclera.
Grade 4
State the function of each partE.g. the retina contains light receptors; the optic nerve carries impulses to the brain.
Grade 5
Describe how the pupil changes with lightThe pupil widens in dim light to let more light in and narrows in bright light.
Quick recall
Cover the answers and test yourself. The app has these as flashcards that come back just before you'd forget them.
Name the part of the eye that carries impulses from the retina to the brain.
Optic nerve
Sample questions
Written for this site in the style of AQA exam questions. They are not taken from real past papers.
Question 1Easy5 marks
The eye is a sense organ containing receptors that are sensitive to light intensity and colour.
(a) Which part of the eye contains the light receptors? Tick (✓) one box.[1]
Cornea
Iris
Lens
Retina
(b) Name the part of the eye that carries impulses from the retina to the brain.[1]
(c) What is the function of the sclera?[1]
(d) What is the function of the iris?[1]
(e) What is the function of the cornea?[1]
Show the answer and mark scheme
(a)Answer: Retina
(b)Answer: Optic nerve
optic nerve
(c)
a tough outer layer that protects the eye
(d)
it controls the size of the pupil / how much light enters the eye
(e)
it lets light into the eye and refracts it
Question 2Medium7 marks
The eye can focus on objects at different distances. This is called accommodation.
(a) Describe how the eye changes to focus on a near object.[3]
(b) Describe how the eye changes to focus on a distant object.[3]
(c) Explain why light must be focused on the retina for a person to see a clear image.[1]
Show the answer and mark scheme
(a)
the ciliary muscles contract
the suspensory ligaments loosen / slacken
the lens becomes thicker / more rounded, so it refracts light more strongly
(b)
the ciliary muscles relax
the suspensory ligaments are pulled tight
the lens is pulled thin, so it refracts light only slightly