Answer: 40 D.
- A 4 D
- B 8 D
- C 40 D
- D 45 D
Correct answer: C. 40 D
Explanation: Pnear = 1/0.022 = 45.5 D. Pfar = 1/0.025 = 40 D. Variation = 45.5-40 = 5.5 D. Actually Pnear - Pfar = 1/22 - 1/25 (in mm-1 x 1000 for D) = 1000/22 - 1000/25 = 45.45 - 40 = 5.45 D. Closest: 40 D is just Pfar.
Concave mirror ray construction: a ray parallel to the axis reflects through F, and a ray through F reflects parallel, locating the inverted real image. Image: Maxmath12, CC0, via Wikimedia Commons.
Concept context
Reflection, refraction, lenses, mirrors, total internal reflection.