Visual Optics Practice Test

To determine the needed spectacle correction for an uncorrected ametrope's right eye when an object is brought to a distance of 40 cm for clarity, we need to understand how the eye focuses light for objects at various distances. In optical terms, the distance of 40 cm corresponds to a convergence point for light rays entering the eye, which means that we need to find the lens power that allows the eye to clearly focus on an object at this distance. The basic formula used to calculate the required lens power (in diopters) is: Lens Power (D) = 1 / Focal Length (m) In this scenario, since the object must be at 40 cm for clarity, we first convert this distance into meters: 40 cm = 0.40 m. The required power is then calculated as: Lens Power (D) = 1 / 0.40 = +2.50 D However, if the individual's uncorrected vision requires a negative power to achieve clarity at this distance, then we are looking for a negative correction. Given the choices, -2.60 DS would indicate that the eye has a greater degree of myopia or uncorrected nearsightedness than +2.50 can