ABO NOCE Practice Test

A plus lens is also known as which type of lens?

1. Cylindrical

2. Concave

3. Convex

4. Spherical

The correct answer is: Convex

A plus lens is known as a convex lens because it is thicker at the center than at the edges. This lens shape causes light rays that pass through it to converge, bringing them to a focal point on the other side of the lens. Convex lenses are commonly used in a variety of optical applications, including magnifying glasses, microscopes, and eyeglasses for hyperopia (farsightedness). The ability of convex lenses to converge light makes them essential in correcting vision and enhancing images. In contrast, a cylindrical lens, which has different curvature in one meridian compared to another, is primarily used to correct astigmatism. Concave lenses, which are thicker at the edges than in the center, diverge light rays and are used to correct myopia (nearsightedness). While "spherical" may describe the shape of some lenses, it does not specifically indicate the converging nature of plus lenses. Thus, the distinction of a plus lens being a convex lens is crucial in understanding its optical properties.