Practice question

**Convex lens image formation**: object beyond 2F (u>2f) real inverted diminished between F and 2F, at 2F same size at 2F, between F and 2F magnified beyond 2F, at F image at infinity, within F virtual erect magnified same side. For f=15 cm, u=30 cm=2f, m = v/u =30/30=1? Actually v=30 cm, m=-1, same size inverted. Magnification: m = 1 + (D/f) . D = 25 cm , f = 4 cm . m = 1 + (25/4) = 1 + 6.25 = 7.25 . Substituting values gives 7.25, which matches expected image position and magnification from mirror/lens formula 1/f = 1/v - 1/u (lens)