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

Explain the resolving power of a microscope.

Some distant star is to be observed by a telescope with an objective lens diameter of $a$, at an angular resolution of $3.0 \times 10^{-7}$ radian. If the wavelength of light from the star reaching the telescope is $500$ nm, the minimum diameter of the objective lens of the telescope is . . . . . . cm. (nearest integer)

The diameter of the objective of the telescope is $0.1 \ m$ and the wavelength of light is $6000 \ \mathring{A}$. Its resolving power would be approximately:

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

The aperture of the objective of a telescope is $24.4 \, cm$. What is the resolving power of this telescope if light of wavelength $2440 \, \mathring{A}$ is used to view the object?