When objects at different distances are seen by the eye, which of the following remains constant?

Options

A. the focal length of the eyes lens
B. the objects distance from the eye lens
C. the radii of curvature of the eye lens
D. the image distance from the eye lens

Explanation

To solve the question of which aspect remains constant when objects at different distances are seen by the eye, we can analyze each option provided:

1. **Focal Length of the Eye's Lens**:
- The focal length of the eye's lens changes depending on the distance of the object being viewed. When viewing distant objects, the lens flattens, increasing the focal length. Conversely, when viewing nearby objects, the lens becomes more curved, decreasing the focal length. Therefore, the focal length does not remain constant.

2. **Object Distance**:
- The object distance refers to how far away the object is from the eye. This distance can vary significantly depending on the object being viewed. Thus, the object distance does not remain constant.

3. **Radii of Curvature of Eye's Lens**:
- The radii of curvature of the eye's lens also change as the eye accommodates for different distances. As the focal length changes, the curvature of the lens must adjust accordingly. Therefore, the radii of curvature do not remain constant.

4. **Image Distance from the Eye's Lens**:
- The image formed by the eye's lens is always projected onto the retina, regardless of the distance of the object. The retina is a fixed distance from the lens of the eye, meaning that the image distance remains constant.

Based on this analysis, the correct answer is that the **image distance from the eye's lens remains constant**.

### Final Answer:
The image distance from the eye's lens remains constant.