$A$ simple microscope is a combination of two lenses in contact. Their powers are $+20$ $D$ and $-4$ $D$. The distance of distinct vision is $25$ cm. When seen through the microscope, the size of an object $3$ mm high is (in $cm$)

To improve the resolving power of a compound microscope, we should:

Given below are two statements: one is labelled as Assertion $A$ and the other is labelled as Reason $R$.
Assertion $A$: For a simple microscope,the angular size of the object equals the angular size of the image.
Reason $R$: Magnification is achieved as the small object can be kept much closer to the eye than $25\, cm$ and hence it subtends a large angle.
In the light of the above statements,choose the most appropriate answer from the options given below:

In a compound microscope,let $u_0$ and $v_0$ be the object distance and image distance respectively. The objective of focal length $f_0$ magnifies a tiny object into a real,inverted image. The linear magnification of the objective is

Fingerprints are observed by the use of

In order to increase the magnifying power of a compound microscope: