Two thin lenses are mounted coaxially on an optical bench
PHYSICS · Multi-part · CBSE · Physics · Ray Optics and Optical Instruments · Ray Optics and Optical Instruments
Problem
Two thin lenses are mounted coaxially on an optical bench. Lens L₁ is a diverging lens with focal length −15cm. Lens L₂ is a converging lens with focal length +20cm and is located 30\,cm to the right of L₁. An illuminated arrow 3.0\,cm tall is placed 12\,cm to the left of L₁.
Ignore the thickness of each lens and assume the principal axes coincide.
(1) Treating L₁ alone, determine (i) the position of the image produced by L₁ relative to L₁ and (ii) the magnification of that image.
(2) Taking the image formed by L₁ as the object for L₂, calculate the position of the final image produced by the two-lens system relative to L₂.
(3) Compute the overall linear magnification of the arrow after light passes through both lenses.
(4) State whether the final image is real or virtual, upright or inverted, and enlarged or reduced with respect to the original arrow. Provide reasoning based on your numerical results.
(5) Qualitatively discuss how increasing the separation between L₁ and L₂ would affect the location and nature (real versus virtual) of the final image, assuming all other parameters remain fixed.