Geometric Optics: Lenses and Mirrors
Optics is a high-yield physics topic for MCAT, especially in the context of the eye and corrective lenses. The thin lens equation: 1/f = 1/do + 1/di, where f is focal length, do is object distance, and di is image distance. Magnification: m = −di/do. A positive di means a real image (same side as the lens as outgoing light); negative di means a virtual image (same side as incoming light). Converging (convex) lenses: positive focal length; can form real or virtual images depending on object distance. Diverging (concave) lenses: negative focal length; always form virtual, upright, reduced images. The power of a lens in diopters: P = 1/f (meters). For the eye: the cornea and lens focus light on the retina. Myopia (nearsightedness) — eyeball too long; corrected with diverging lens. Hyperopia (farsightedness) — eyeball too short; corrected with converging lens.