AQA Biology 4.5.2.3
Defects of the eye
In two common defects, light doesn’t focus on the retina. Find where it lands, then drop in the lens that fixes it.
Triple Science · Foundation tier
Start here
Glasses on.
Look around a classroom at who wears glasses, and when they put them on.
If you had to guess, is it more often to see the board, or to read a book close up?
Ray diagrams
Where does it focus?
In myopia (short sight) and hyperopia (long sight), rays of light do not focus on the retina. Spectacle lenses refract the rays so that they do. Pick a defect, then try each lens.
Myopia: light from a distant object focuses in front of the retina, so the image is blurred. The eyeball is usually too long, or the lens too curved.
Read this one: which defect is it, and which lens corrects it?
Pick an answer.
Treatments
Ways to correct it.
Spectacles are the usual treatment. 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. Tap each for a benefit and a risk.
How a normal eye focuses on near and distant objects: The eye.
Think again · short sight, near things?
“Short-sighted means you can’t see things that are close.”
Your call
ChooseWhat can’t a short-sighted person see clearly?
Sort
Myopia or hyperopia?
Place each one.
Tap a card, then tap the box it belongs in. Tap a placed card to take it back.
Command words in this lesson
- Interpret
- A ray diagram: where the rays focus and what that means.
- Explain
- How a lens moves the focus onto the retina.
- Evaluate
- Treatments, with a benefit and a risk for each, then a judgement.
Key fact
Myopia: distant objects blurred, light focuses in front of the retina, concave lens. Hyperopia: near objects blurred, focus behind the retina, convex lens.
Key note · AQA 4.5.2.3 (Triple)
Defects of the eye
- Myopia and hyperopia: rays of light do not focus on the retina.
- Myopia (short sight): distant objects blurred, focus in front of the retina, corrected with a concave lens.
- Hyperopia (long sight): near objects blurred, focus behind the retina, corrected with a convex lens.
- New technologies: hard and soft contact lenses, laser surgery to change the shape of the cornea, a replacement lens.
Photograph this card. Tomorrow, cover it and say each line first.
Previous and next
Connects to
Ask MrBadmus
Getting concave and convex the wrong way round?
Ray diagrams are schematic and not to scale.