In a compound microscope,the magnification will be large if the focal length of the eyepiece is:

In a compound microscope,the focal length and aperture of the objective lens used are,respectively:

What are the objective and the eye-piece in an optical instrument?

$A$ 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?

$A$ card sheet divided into squares each of size $1 \, mm^{2}$ is being viewed at a distance of $9 \, cm$ through a magnifying glass (a converging lens of focal length $10 \, cm$) held close to the eye.
$(a)$ What is the magnification produced by the lens? How much is the area of each square in the virtual image?
$(b)$ What is the angular magnification (magnifying power) of the lens?
$(c)$ Is the magnification in $(a)$ equal to the magnifying power in $(b)$? Explain.

$A$ thin convex lens of focal length $5 \, cm$ is used as a simple microscope by a person with a normal near point of $25 \, cm$. What is the magnifying power of the microscope?