A convex lens has f = +20 cm. An object is placed (a) 60 cm, (b) 30 cm, (c) 10 cm to its left. Find v and describe each image. Sign convention: u negative to the left. 1/v = 1/f + 1/u. Case (a): u = −60. 1/v = 1/20 − 1/60 = (3−1)/60 = 2/60 → v = +30 cm. Real image 30 cm right of lens, between F and 2F. m = v/u = 30/(−60) = −0.5: inverted, half size (camera-like). Case (b): u = −30. 1/v = 1/20 − 1/30 = (3−2)/60 = 1/60 → v = +60 cm. Real, inverted, m = 60/(−30) = −2: enlarged 2× beyond 2F (projector-like). Case (c): u = −10 (inside F). 1/v = 1/20 − 1/10 = (1−2)/20 = −1/20 → v = −20 cm. Virtual image 20 cm left (same side as object). m = v/u = (−20)/(−10) = +2: upright, doubled — the magnifying-glass effect. The sign flip of v marks the real/virtual boundary at u = −f.