Problem 35.2: Hidden lenses, mixed sources

Object A: Restart

Object B: Restart

Object C: Restart

Object D: Restart

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Four regions are hidden by curtains. The light sources are dragable. The arrow represents an object, and the fainter arrow represents its image (position is given in meters).

  1. What is behind each curtain?
  2. Rank the objects in terms of their focal lengths, from smallest to largest (most negative to most positive).

Problem authored by Melissa Dancy.