When a plus lens is moved closer to the eye, what happens to its perceived power?

When a plus lens is moved closer to the eye, the perceived power actually increases. This occurs due to the concept of magnification associated with converging lenses. A plus lens, which is convex, causes light rays to converge and therefore has a positive focal length.

As the lens moves closer to the eye, the effective distance from the eye to the lens decreases, which alters the way the brain interprets the light rays entering the eye. The focal point of the lens also shifts, effectively increasing the degree of convergence and thus the perceived power. This is related to the formula used in optics where the effective power of a lens is influenced by both the lens power and its distance from the eye.

It’s essential to recognize that the effect of distance on lens power is a fundamental principle in optics related to how lenses function in vision correction. Understanding this principle helps in various applications, including fitting lenses and understanding how patients perceive their vision with different lens configurations.