Задача id13159

Light from a point source located on the optical axis of the lens behind its focus, after passing through the lens, is reflected back from a concave spherical mirror with a spherical radius R and, having passed through the lens a second time, produces an image. At what points on the optical axis can a mirror be placed so that the image coincides with the object itself? How will the image move if the mirror is moved between these points?

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