Задача id13182

The light source is placed at a distance L > 8F from the screen. Two identical collecting lenses with focal lengths equal to F are inserted between the source and the screen. At what positions of the lenses will the source be imaged in full size? What is the illuminance ratio of the images? When calculating illumination, sources are considered small compared to the diameter of the lens, and its diameter is small compared to its focal length.

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