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As my textbook stated we use a convex lens of small focal length $f$ to keep an object at a distance such that the image is produced at a distance $D$ (our least distant clear vision point is around $25\ {\rm cm}$).

Then the magnification that comes assuming non-marginal rays is $1 + \frac{D}{f}$.

Why can't we keep reducing $f$ in order to get more magnification? Why is there a limit to which a simple microscope magnification?

ohneVal
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aryan bansal
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  • Diffraction limits. You can see objects from which light bounces back Optical microscope magnification limits?. Thus max resolution is bound to visible light wavelength, which is $\approx 0.2 \mu m$. By rough analogy, try to measure size of a cup by smashing pillow into it 2. Chromatic aberration. Different wavelengths will focus onto different focal points, so for even smaller focal lengths you will need to add layer with complementary dispersion properties, thus making it a non-simple microscope.
    • – Agnius Vasiliauskas Aug 03 '20 at 13:36