Light of wavelength $\lambda$ is coming from a star. What is the limit of resolution of a telescope whose objective has diameter $r$?

If the numerical aperture $(NA)$ of a microscope is increased,then its:

The diameter of the objective of a telescope is $1 \ m$. Its resolving limit for light of wavelength $4538 \ \text{Å}$ will be:

The resolving power of an astronomical telescope is $0.2$ seconds. If the central half portion of the objective lens is covered,the resolving power will be......$sec$

If the wavelengths of light used in an optical instrument are $\lambda_1 = 4000 \, \mathring A$ and $\lambda_2 = 5000 \, \mathring A$,what will be the ratio of their resolving powers?

$A$ telescope has an objective lens of $10\, cm$ diameter and is situated at a distance of $1\, km$ from two objects. The minimum distance between these two objects which can be resolved by the telescope,when the mean wavelength of light is $5000\,\mathring{A}$,is the order of