Question

For which colour of magnifying power of a simple microscope is highest? For which colour is it lowest?

Answer 1

The geometry of the optical system is related to the magnifying power, or amount to which the thing being examined seems enlarged, and the field of view, or size of the object that can be viewed. Magnification is determined by focal length, and focal length is determined by colour, and different colours have different wavelengths (i.e., different refractive indices).

Complete answer:
Blue (or violet) scores the highest, while red scores the lowest.
The magnifying power of a basic microscope is given by $M{\text{ }} = \dfrac{{1{\text{ }} + {\text{ }}D}}{f}$ .
$D =$ The shortest distance of clear vision for a typical eye $= 25{\text{ }}cm$ and $f =$ stands for focal length.
The value of f varies with colour (because of varying refractive indexes). The bending is more pronounced for blue (or violet) and less so for red. This is referred to as chromatic aberration.
As a result, the focal length for red light is greater and that for blue (or violet) light is lower.
A smaller $f$ results in a greater $M$ value.

Note:
A simple microscope is just a magnifying glass that consists of a single convex lens with a short focal length that magnifies the object by angular magnification. It should be noted that the minimum value of magnifying power of a simple microscope is $8$ and the maximum value of magnifying power of a simple microscope is $9$ .