Problem 3
A thin converging lens in air has focal length f>0. An upright real object of height H lies on the principal axis at distance u>f from the optical center; use the convention that a real image on the opposite side has v>0. Neglect lens thickness and aberrations. (a) Establish the relation among u, v, and f. (b) Find v and identify the image as real or virtual. (c) Find signed magnification m and signed image height. Use SI units throughout and treat components as ideal exactly as specified. State sign conventions when writing equations and retain units in final results.
problems.proof.stepOf
problems.proof.analysis
The equation follows by applying the physical law to the chosen system; ideal constraints link the variables. Signs must remain consistent with the defined directions.
problems.proof.pitfall. Pitfall: do not change sign conventions between equations; a negative sign may encode direction rather than an invalid result.