• summary_type: concept
• word_count: 180

A simple microscope (magnifying glass) is a single convex lens producing a virtual, erect, magnified image. Magnifying power: M = 1 + D/f (image at near point) or M = D/f (image at infinity, relaxed eye), where D = 25 cm. A compound microscope uses two convex lenses: a short-focal-length objective (creates real, magnified, inverted intermediate image) and an eyepiece (acts as simple microscope on the intermediate image). Total magnification: M = (L/f_o)(1 + D/f_e) at near point, or M = (L/f_o)(D/f_e) at infinity, where L is the tube length. For maximum magnification, both f_o and f_e should be small while L should be large. The resolving power of a microscope is 2n sinθ/(1.22λ), enhanced by oil immersion (increasing n). JEE problems typically ask for magnification calculations or conceptual questions about the role of each lens.