Practice question

**Compound microscope** M = m_o × M_e, objective magnification m_o = v_o/u_o ≈ L/f_o, L tube length, eyepiece M_e = 1+D/f_e (image at D) or D/f_e (infinity). Objective forms real inverted magnified image at focal plane of eyepiece, eyepiece acts as simple microscope magnifying it. f = 20 cm , u = -12 cm . (1/v) + (1/-12) = (1/20) ⇒ (1/v) = (1/20) + (1/12) = (3 + 5/60) = (8/60) = (2/15) . v = 7.5 cm . Magnification: m = -(v/u) = -(7.5/-12) = 0.625 . Substituting values gives 0.625, which matches expected image position and magnification from mirror/lens formula 1/f =