$A$ man can clearly see two poles at a distance of $11 \, km$. What should be the minimum distance between the poles in $m$?

The resolving power of a telescope whose lens has a diameter of $1.22 \ m$ for a wavelength of $5000 \ \mathring{A}$ is

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?

Assertion $(A):$ To increase the resolving power of a telescope,the aperture $(a)$ of the objective lens should be large.
Reason $(R):$ The resolving power of a telescope is given by $\frac{a}{1.22 \lambda}$.

The human eye has an approximate angular resolution of $\theta = 5.8 \times 10^{-4} \text{ rad}$ and a typical photo printer prints a minimum of $300 \text{ dpi}$ (dots per inch, $1 \text{ inch} = 2.54 \text{ cm}$). At what minimal distance $d$ should a printed page be held so that one does not see the individual dots (in $\text{ cm}$)?

The diameter of the objective lens of a telescope is $250\, cm$. For light of wavelength $600\, nm$ coming from a distant object, the limit of resolution of the telescope is close to: