Practice question

**Lens formula** 1/f = 1/v - 1/u, f focal length (m), u object distance, v image distance, sign: u negative if object left of lens in Cartesian convention, magnification m = v/u, real image inverted m negative, virtual erect m positive. Power P = 1/f (diopters D), f in meters, +5 D means f=0.2 m=20 cm converging. Outside the focal point, a convex lens converges rays to a point on the opposite side, forming a real image. Inside the focal point, rays diverge after refraction, appearing to come from a point on the same side, resulting in a virtual image instead. Substituting values gives Due