Eye defects: restore focus to the retina
| English | Français |
|---|---|
| myopia/maɪˈəʊpɪə/ | myopia |
| hyperopia/ˌhaɪpəˈrəʊpɪə/ | hyperopia |
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.
- Start with a prediction. State the quantities or features you would compare, then decide what evidence could distinguish two explanations.
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?
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.
Match each technical term to its precise meaning.
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.
- 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?
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.
Work from known quantities
- State the known values and their units. Choose the relation because its assumptions fit this case, then rearrange before substitution.
- 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.
A model displacement is drawn as 18 mm at magnification 6. Calculate the represented displacement. Use the same sequence: known quantities → model → relation → substitution → unit and interpretation.
A model displacement is drawn as 18 mm at magnification 6. Calculate the represented displacement.
The result is 3 mm. 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.
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.
- Return to the original observation. Explain what the result supports, which conditions it assumes, and one way to test a competing explanation.
Myopia and hyperopia are corrected by the same change in ray direction in every model. This claim is false: 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.
Eye defects: restore focus to the retina: 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.
Myopia and hyperopia are corrected by the same change in ray direction in every model.
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.
Short sightedness with distant-object rays focused before the retina: write the technical term.
myopia means Short sightedness with distant-object rays focused before the retina.