For observing a cricket match,a binocular is preferred to a terrestrial telescope because

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

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?

In a simple microscope,if the final image is located at infinity,then its magnifying power is:

$A$ microscope has an objective of focal length $1 \ cm$ and an eyepiece of focal length $6 \ cm$. If the tube length is $30 \ cm$ and the image is formed at the least distance of distinct vision,what is the magnification produced by the microscope? Take $D = 25 \ cm$.

$A$ 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 $cm$)