The image formed by the objective lens of a compound microscope is:

$A$ man uses a thin convex lens of focal length $5 \, cm$ as a magnifying glass. He reads a book by holding it close to his near point of $25 \, cm$. What are the closest and farthest distances at which he can keep the book from the lens to read clearly?

In a Ramsden eyepiece, two plano-convex lenses, each of focal length $f$, are separated by a distance of $d = 2f/3$. If the separation distance is $12 \ cm$, what is the equivalent focal length (in $cm$) of the eyepiece?

$A$ 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 $cm$)

In a compound microscope,the focal lengths of the objective and eye lens are $2.5 \, cm$ and $5 \, cm$ respectively. An object is placed at $3.75 \, cm$ in front of the objective. If the final image is formed at the least distance of distinct vision,then the distance between the two lenses (length of the microscope tube) is.......$cm$.

Write the equation of magnification for a simple microscope when the image is formed at the near point.