We wish to make a microscope with the help of two positive lenses,both with a focal length of $20\, mm$ each,and the object is positioned $25\, mm$ from the objective lens. How far apart should the lenses be so that the final image is formed at infinity?......$mm$

$A$ compound microscope consists of an objective lens of focal length $2.0 \;cm$ and an eyepiece of focal length $6.25 \;cm$ separated by a distance of $15\;cm$. How far from the objective should an object be placed in order to obtain the final image at
$(a)$ the least distance of distinct vision $(25\;cm)$,and
$(b)$ at infinity? What is the magnifying power of the microscope in each case?

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.......$cm$.

In which of the following is the final image erect?

$A$ microscope consists of an objective of focal length $1.9 \,cm$ and an eyepiece of focal length $5 \,cm$. The two lenses are kept at a distance of $10.5 \,cm$. If the image is to be formed at the least distance of distinct vision, the distance at which the object is to be placed before the objective is (least distance of distinct vision is $25 \,cm$). (in $\,cm$)

$A$ compound microscope consists of an objective lens of focal length $1 \, cm$ and an eyepiece of focal length $5 \, cm$ with a separation of $10 \, cm$. The distance between an object and the objective lens,at which the strain on the eye is minimum,is $\frac{n}{40} \, cm$. The value of $n$ is $....$