Video narration
How can two ordinary lenses produce such enormous magnification? Start with familiar convex-lens picture. The objective-the first lens-takes the tiny object and forms a real, enlarged intermediate image. That image becomes the object for the eyepiece. Let L be the tube length, and f_o the objective focal length. The usual ray-diagram approximation gives the objective magnification m_o ≈ L/f_o. Now the eyepiece acts like a magnifying glass on that intermediate image. With the final image at infinity, called normal adjustment, its magnification is m_e = D/f_e, where D is the least distance of distinct vision and f_e its focal length. Key point: the two lenses do not add their magnifications. The eyepiece enlarges an image already enlarged by the objective, so the factors multiply. Therefore, using magnitudes, M = m_o × m_e = (L/f_o)(D/f_e). Two ordinary lenses create the microscope's enormous magnification through multiplication.