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

$A$ scientist is observing a bacteria through a compound microscope. For better analysis and to improve its resolving power,he should: (Select the best option)

The focal lengths of the objective and the eye-piece of a compound microscope are $2.0 \, cm$ and $3.0 \, cm$ respectively. The distance between the objective and the eye-piece is $15.0 \, cm$. The final image formed by the eye-piece is at infinity. The two lenses are thin. The distances in $cm$ of the object and the image produced by the objective measured from the objective lens are respectively:

$A$ 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 $15 \, cm$. What is the magnifying power when the final image is formed at the least distance of distinct vision $(25 \, cm)$?

$A$ card sheet divided into squares each of size $1 \; mm^{2}$ is being viewed through a magnifying glass (a converging lens of focal length $9 \; cm$) held close to the eye. What should be the distance between the object and the magnifying glass if the virtual image of each square in the figure is to have an area of $6.25 \; mm^{2}$? Would you be able to see the squares distinctly with your eyes very close to the magnifier?

$A$ simple microscope is used to see an object first in blue light and then in red light. Due to the change from blue to red light, its magnifying power