Practice question

**Two lenses in contact** behave as single lens with power sum, magnification product m = m₁×m₂. For f₁=20 cm (P₁=5 D), f₂=-20 cm (P₂=-5 D) in contact, P=0, F infinite, afocal system, beam emerges parallel, principle of corrective lenses for myopia/hypermetropia. For a concave lens, the image is always virtual, erect, and diminished. As the object moves closer, the image size increases (though still smaller than the object), and the image moves closer to the lens, but remains on the same side as the object. Substituting values gives Image size increases but remains diminished, which matches expected image position and magnification from mirror/lens formula 1/f