Question

For which colour the magnifying power of a simple microscope is highest

Answer 1

Highest for blue (or violet ) and lowest for red.

For a simple microscope the magnifying power is given by

M = 1 + D / f

D = The least distance of distinct vision = 25 cm for a normal eye

f = focal length

f is different for different colors ( due to different refractive indexes ) . The bending is more for blue(or violet) and least for red. This phenomenon is known as chromatic aberration.

Hence the focal length corresponding to red light is larger and that for blue(or violet) is smaller.

Smaller f gives larger value of M