Certified Paraoptometric Practice Test

Which type of lens converges parallel light?

1. Prism

2. Concave (-)

3. Pl-cylinder

4. Convex (+)

The correct answer is: Convex (+)

A convex lens is designed to converge parallel rays of light towards a focal point. This optical property is a result of the lens's shape, which is thicker in the middle than at the edges. When parallel light waves, such as those from a distant object, enter the lens, the curvature of the lens bends the light rays inward due to refraction. The converged rays meet at a point known as the focal point, enabling functionalities such as magnification in glasses and cameras. In contrast, a prism is used to refract light but does not have the same converging effect as a convex lens. A concave lens diverges light rays, making them appear to originate from a virtual focal point behind the lens, while a cylindrical lens focuses light differently depending on the orientation of its curvature. None of these types have the same converging ability for parallel light as a convex lens.