For distance vision, the lens needs to be
[选择]
thick and spherical
thin and elliptical
thin and spherical
thick and ellipitical
. For near vision, the lens must be
[选择]
thin and spherical
thin and ellipitical
thick and spherical
thick and elliptical
.

Question

For distance vision, the lens needs to be 
[选择]
thick and spherical
thin and elliptical
thin and spherical
thick and ellipitical
 . For near vision, the lens must be 
[选择]
thin and spherical
thin and ellipitical
thick and spherical
thick and elliptical
 .

BlackTom AI · Accepted Answer

The question presents two separate selections related to lens shape for vision: one for distance vision and one for near vision. Below, I evaluate each possible option in turn.

Distance vision options:
- Option A: thick and spherical. A thick lens would increase power, which is not typically required for distant objects where relaxed accommodation and minimal refractive power are needed. This makes the statement incorrect for distance vision.
- Option B: thin and elliptical. A thin lens is generally associated with lower refractive power, which is more appropriate for distant vision only if the eye is emmetropic or less myopic. Elliptical surfaces represent a non-symmetric curvature and are not standard descriptors used to describe a normal spherical correction for distance vision, so this is not the typical configuration.
- Option C: thin and spherical. For distance vision, the eye requires low refractive power and a symmetric, spherical surface is the common idealized description of a relaxed lens or a minimally powered corrective lens. This aligns with usual understanding of distance correction in optics.
- Option D: thick and elliptical. A thick, ellipsoidal lens would imply higher complexity and more refractive power, which is not characteristic of distance vision corrections. This makes it incorrect.

Near vision options:
- Option A: thin and spherical. Near vision correction usually requires increased optical power and a compact surface, but a thin lens with spherical form is insufficient to provide the necessary convergence for close objects. Therefore, this option is incorrect for near vision.
- Option B: thin and elliptical. While an elliptical surface can vary curvature, the key requirement for near vision is higher power, and a thin lens alone without added thickness or higher curvature is not adequate. This option is not consistent with typical near-vision needs.
- Option C: thick and spherical. Near vision demands more refractive power due to accommodation, and a thicker lens with a spherical surface provides greater convergence. This description matches the expected near-corrective configuration.
- Option D: thick and elliptical. Although thick and elliptical surfaces can yield high power, the common, standard description emphasizes a thick, spherical surface for straightforward near-vision correction; elliptical shapes are less conventional in this simple comparison and could imply aberrations or nonstandard design. This makes it less typical and thus incorrect in this context.

Given the provided answer set aligns with the conventional reasoning, the distance-vision correct choice corresponds to 'thin and spherical', and the near-vision correct choice corresponds to 'thick and spherical'. The other options introduce less appropriate power levels or unconventional surface geometries for the respective distance and near vision scenarios.

BIOLOGY 211-B09C HW #14: Visual System

For distance vision, the lens needs to be [选择] thick and spherical thin and elliptical thin and spherical thick and ellipitical . For near vision, the lens must be [选择] thin and spherical thin and ellipitical thick and spherical thick and elliptical .

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