Eye defects: restore focus to the retina
הוצג| English | משמעות |
|---|---|
| myopia/maɪˈəʊpɪə/ | קוצר ראייה |
| hyperopia/ˌhaɪpəˈrəʊpɪə/ | קוצר ראייה (היפרופיה) |
What would explain this observation?
- A blurry image can arise because rays focus before or beyond the retina. A corrective lens changes their direction before they reach the eye’s own focusing structures.
Build the model
- In myopia 近视, or short sightedness, rays from a distant object focus in front of the retina.
- A diverging spectacle lens changes the incoming rays so that the eye focuses them on the retina.
- In hyperopia 远视, or long sightedness, rays from a near object would focus behind the retina.
- A converging spectacle lens helps bring the focus forwards onto it.
- myopia: Short sightedness with distant-object rays focused before the retina.
- hyperopia: Long sightedness with near-object rays focused behind the retina.
Which lens corrects the supplied myopia model?
רמת קושי 1/5 · 100 מטבעות + בונוס קטן בהשלמה הראשונה היום
Myopia focuses rays in front of the retina because the eye converges too strongly; a diverging lens spreads the rays so the focus moves back onto the retina. Covering the retina blocks vision, and extra convergence worsens the focus.
Match each technical term to its precise meaning.
רמת קושי 2/5 · 140 מטבעות + בונוס קטן בהשלמה הראשונה היום
Use the definitions to distinguish related quantities and processes.
Choose evidence that can test it
- Interpret the ray diagram using the position of the retina and focus, then the effect of the external lens.
- The specification also identifies hard and soft contact lenses, laser surgery changing corneal shape and a replacement lens in the eye.
- These are correction technologies; choosing between them needs individual professional assessment rather than a classroom rule.
In the lab: Trace supplied rays with a ruler and label before-retina, on-retina or behind-retina focus. Compare diagrams with the same orientation. Use safe model lenses and a screen if teacher-approved, never a laser directed at an eye. Explain how refraction corrects the indicated defect without prescribing a lens strength.
Which two habits make the investigation or model in this case more defensible?
רמת קושי 2/5 · 140 מטבעות + בונוס קטן בהשלמה הראשונה היום
Stating the conditions and assumptions lets others repeat the work exactly, and recording the supporting evidence lets them check the conclusion. Hiding disagreeing results removes the evidence that could challenge a wrong conclusion, and one measurement can never establish a wider claim.
Work from known quantities
- Known: a supplied diagram is drawn at five times the model scale.
- A drawn 10 mm distance between a focus and retina represents 2 mm in that model.
- This converts drawing size only.
- It does not reveal a spectacle power, an eye diagnosis or a real distance inside someone’s eye.
Your turn: A model displacement is drawn as 18 mm at magnification 6. Calculate the represented displacement.
A model displacement is drawn as 18 mm at magnification 6. Calculate the represented displacement.
רמת קושי 2/5 · 140 מטבעות + בונוס קטן בהשלמה הראשונה היום
The result is 3 mm. Known: drawn displacement 18 mm at magnification 6. Use real size = drawn size / magnification. Displacement = 18/6 = 3 mm in the model. The conversion concerns the drawing only.
Check the conclusion and its limits
- Myopia is corrected with a diverging lens, while the supplied hyperopia model uses a converging lens.
- A retina drawn on the wrong side can reverse an interpretation.
- Accommodation is the eye changing its own lens shape; a spectacle lens is an external correction.
Not true: Myopia and hyperopia are corrected by the same change in ray direction in every model. Myopia needs a diverging lens; hyperopia needs a converging lens. The ray changes are opposite, so one correction cannot fix both.
- In myopia, or short sightedness, rays from a distant object focus in front of the retina.
- Interpret the ray diagram using the position of the retina and focus, then the effect of the external lens.
- Watch for: myopia is corrected with a diverging lens, while the supplied hyperopia model uses a converging lens.
Myopia and hyperopia are corrected by the same change in ray direction in every model.
רמת קושי 1/5 · 100 מטבעות + בונוס קטן בהשלמה הראשונה היום
Myopia needs a diverging lens; hyperopia needs a converging lens. The ray changes are opposite, so one correction cannot fix both.
Short sightedness with distant-object rays focused before the retina: write the technical term.
רמת קושי 1/5 · 100 מטבעות + בונוס קטן בהשלמה הראשונה היום
myopia means Short sightedness with distant-object rays focused before the retina.