Final answer:
Concave lenses diverge light creating always smaller, virtual images, whereas convex lenses can converge light to form real or virtual images that can be either larger or smaller than the object.
Step-by-step explanation:
The primary difference between concave and convex thin lenses lies in how they manipulate light. A convex lens also called a converging lens, directs light rays to intersect at a focal point, producing real or virtual images that can be larger or smaller than the object. On the contrary, a concave lens, known as a diverging lens, spreads light rays outward, resulting in only virtual images that are always smaller than the object. Convex lenses are often used in applications like cameras or projectors, where they can either magnify or reduce the size of an image. In contrast, concave lenses are typically used in glasses for individuals with myopia (nearsightedness), as they help to diverge light rays and reduce the image's size to correct the viewer's vision. Both types of lenses obey geometric optics principles, like the thin-lens equation, to predict the characteristics of the images they form, such as real versus virtual, inverted versus upright, and size variations compared to the object.