A thin converging lens L1 (focal length +15 cm) and a thin diverging lens L2 (focal length −20 cm) are mounted 10 cm apart on a common optic axis. A 2.0 cm-tall arrow object is placed 30 cm to the left of L1.
Assume ideal thin-lens behavior and neglect the thickness of the lenses.
(a) Without performing explicit numerical calculations, determine whether the image produced by L1 alone is real or virtual, upright or inverted, and larger or smaller than the object. Justify each aspect of your answer using the object’s position relative to the focal length of L1.
(b) Explain whether the image formed by L1 serves as a real object or a virtual object for L2, given the 10 cm separation between the lenses. Support your reasoning with reference to the location of that image relative to L2.
(c) Based on your answers to parts (a) and (b), predict the orientation (upright or inverted) of the final image formed after L2 relative to the original object. Provide a qualitative explanation that traces the sign of the overall magnification through both lenses.
(d) Describe one specific adjustment to the object distance that would cause the final image to change from virtual to real. Explain why this adjustment has the stated effect.