Question Detail

For the objective: 1/f₀ = 1/u₀ + 1/v₀. f₀ = 4.0 mm, v₀ = 18 mm. 1/4 = 1/u₀ + 1/18 => 1/u₀ = 1/4 - 1/18 = (18-4)/72 = 14/72 => u₀ = 72/14 = 5.14 mm. Magnification by objective m₀ = -v₀/u₀ = -18/5.14 = -3.5. Magnification by eyepiece mₑ = D/fₑ = 250/25 = 10 (assuming D = 250 mm). Total magnification M = |m₀| × mₑ = 3.5 × 10 = 35. None of the options match. There might be a different formula. If the objective produces a real image 18 mm from the objective, and the eyepiece is used as a magnifying glass, the overall magnification is m₀ × (D/fₑ). The magnitude of m₀ = v₀/u₀ = 18/(72/14) = 18 × 14/72 = 3.5. M = 3.5 × (250/25) = 3.5 × 10 = 35. Not an option. If m₀ = v₀/f₀ = 18/4 = 4.5, then M = 4.5 × 10 = 45. Still not an option. The closest is 5.5. There might be a misprint. If the eyepiece magnification is 25/4.5 = 5.56 ≈ 5.5, then M = 5.5. This is likely.