Final answer:
To correct the inability to focus on distant objects, a convex or converging lens should be used to increase the eye's optical power for distant vision.
Step-by-step explanation:
If the lens of the eye cannot adjust enough to focus on a distant object, a converging lens should be added to the optical system. A converging lens, also known as a convex lens, is useful because it can increase the optical power of the eye, making it easier to focus on distant objects. This type of corrective lens helps in bringing the image into focus on the retina when the eye's own lens is unable to do so due to its insufficient focal power. In contrast, nearsightedness (myopia) is corrected with a diverging lens (concave lens), which reduces the optical power so that distant objects can be focused properly.