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Course: MCAT > Unit 3

Lesson 1: Chemical and physical sciences practice passage questions

Using scallops to correct vision


The human eye focuses light using its lens, which alters the path of light so that the image is produced on the retina. Scallops, a type of saltwater clam, has numerous eyes that similarly have a lens and retina. However, the distance between the two structures is negligible, which makes it impossible for the lens to focus light on the retina. This issue is circumnavigated by the fact that past the retina, scallops have a structure called an argentea, which is a type of spherical mirror. This mirror reflects the light back on the retina, effectively providing enough space for the lens to fulfill its function.
A researcher is interested in synthesizing an artificial argentea for patients suffering from axial hyperopia, in which the eyeball is too small, resulting in the image focusing behind the retina. In a laboratory setting, she investigates the properties of the images created by a miniature curved mirror. The lab set up consists of a curved parabolic mirror that is reflective on both sides and table upon which a light source can be placed at different distances from the mirror on either side. The lab set up is shown in the diagram. The point 3 represents the center of curvature of the curved mirror. The point 4 represents the focal point of the curved mirror.
Figure 1. The laboratory setup the researcher is using.
Which of the following light source locations would create the smallest possible real image?
Choose 1 answer: