Accommodation: near and distant objects
| English | 中文 | Pinyin |
|---|---|---|
| accommodation/əˌkɒməˈdeɪʃn/ | 调节作用 | tiáo jié zuò yòng |
| suspensory ligament/səˈspensəri ˈlɪɡəmənt/ | 悬韧带 | xuán rèn dài |
What would explain this observation?
- A close object and a distant object need different lens shapes to form a focused image on the same retina. Trace muscle, ligament and lens changes in order.
- Start with a prediction. State the quantities or features you would compare, then decide what evidence could distinguish two explanations.
Build the model
- Accommodation 调节作用 is changing the lens shape to focus on objects at different distances. For a near object, ciliary muscles contract, suspensory ligaments 悬韧带 loosen and the lens becomes thicker, refracting light more strongly. For a distant object, ciliary muscles relax, the ligaments are pulled tight and the lens is pulled thin, refracting light less strongly.
- accommodation: Changing lens shape to focus on near or distant objects; suspensory ligament: A connection transmitting tension that affects the lens shape.
Which set of changes focuses on a near object?
The lens does not actively pull itself into shape like a muscle. Explain the mechanical connection: ciliary-muscle action changes tension in the suspensory ligaments, allowing or pulling the elastic lens into the appropriate shape. A change in pupil size alone does not supply the required accommodation explanation.
Match each technical term to its precise meaning.
Use the definitions to distinguish related quantities and processes.
Choose evidence that can test it
- The lens does not actively pull itself into shape like a muscle. Explain the mechanical connection: ciliary-muscle action changes tension in the suspensory ligaments, allowing or pulling the elastic lens into the appropriate shape. A change in pupil size alone does not supply the required accommodation explanation.
- Use a labelled paper or elastic-lens model under teacher supervision. Compare near and far configurations and annotate the three linked changes. Interpret ray diagrams by checking that rays focus on the retina. A diagram should clearly distinguish focusing from the separate bright/dim pupil response; do not apply pressure or chemicals to a real eye.
Which two habits make the investigation or model in this case more defensible?
Use a labelled paper or elastic-lens model under teacher supervision. Compare near and far configurations and annotate the three linked changes. Interpret ray diagrams by checking that rays focus on the retina. A diagram should clearly distinguish focusing from the separate bright/dim pupil response; do not apply pressure or chemicals to a real eye.
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 drawing magnifies a model lens dimension tenfold. A 25 mm drawn thickness represents 2.5 mm in the stated model; a 15 mm drawing represents 1.5 mm. The geometrical comparison shows which model is thicker but does not give a real person’s lens dimensions or calculate focusing power.
A model lens thickness is drawn as 28 mm at magnification 8. Calculate the represented thickness. Use the same sequence: known quantities → model → relation → substitution → unit and interpretation.
A model lens thickness is drawn as 28 mm at magnification 8. Calculate the represented thickness.
The result is 3.5 mm. Known: a supplied drawing magnifies a model lens dimension tenfold. A 25 mm drawn thickness represents 2.5 mm in the stated model; a 15 mm drawing represents 1.5 mm. The geometrical comparison shows which model is thicker but does not give a real person’s lens dimensions or calculate focusing power.
Check the conclusion and its limits
- Near focusing uses contracted ciliary muscles and loose ligaments, not the reverse. For distance, tightening the ligaments pulls the lens thin. Drawing thickness and actual thickness need a stated scale. This section does not require a clinical eye test or a spectacle prescription.
- Return to the original observation. Explain what the result supports, which conditions it assumes, and one way to test a competing explanation.
For near focus the suspensory ligaments become tighter and pull the lens thinner. This claim is false: Near focusing uses contracted ciliary muscles and loose ligaments, not the reverse. For distance, tightening the ligaments pulls the lens thin. Drawing thickness and actual thickness need a stated scale. This section does not require a clinical eye test or a spectacle prescription.
Accommodation: near and distant objects: The lens does not actively pull itself into shape like a muscle. Explain the mechanical connection: ciliary-muscle action changes tension in the suspensory ligaments, allowing or pulling the elastic lens into the appropriate shape. A change in pupil size alone does not supply the required accommodation explanation.
For near focus the suspensory ligaments become tighter and pull the lens thinner.
Near focusing uses contracted ciliary muscles and loose ligaments, not the reverse. For distance, tightening the ligaments pulls the lens thin. Drawing thickness and actual thickness need a stated scale. This section does not require a clinical eye test or a spectacle prescription.
Changing lens shape to focus on near or distant objects: write the technical term.
accommodation means Changing lens shape to focus on near or distant objects.