The power of two convex lenses $A$ and $B$ are $8$ diopters and $4$ diopters respectively. If they are to be used as a simple microscope,the magnification of

The focal length of the objective and eye lenses of a microscope are $1.6 \, cm$ and $2.5 \, cm$ respectively. The distance between the two lenses is $21.7 \, cm$. If the final image is formed at infinity,what is the linear magnification?

If we need a magnification of $375$ from a compound microscope of tube length $150\; mm$ and an objective of focal length $5\; mm$,the focal length of the eye-piece should be close to.....$mm$.

$A$ student measures the thickness of a human hair by looking at it through a microscope of magnification $100$. He makes $20$ observations and finds that the average width of the hair in the field of view of the microscope is $3.5 \; mm$. What is the estimate on the thickness (in $mm$) of hair?

To obtain a magnified image at the distance of distinct vision $(D)$ using a simple microscope,the object should be placed:

$A$ 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?