Explain resolving power for optical instruments and explain resolving power of telescopes.

Explanation

Due to diffraction phenomenon in optic instrument it is difficult to see objects and i images that are too close.
he angular resolution of the telescope determined by the objective of the telescope b increasing the magnification through the ey piece, resolution does not get. Eye piece increas the magnification produced by objective.
When a parallel beam of light is incident on convex lens due to this lens the ray beam focus on a point but due to diffraction it will t focus in a finite area instead of being focus : one point. This is shown in figure.

Here due to convex lens dark and bright ring are obtained simultaneously around the centra bright region. These ring is called Airy.s rings.
The radius of the central bright region is if fi the focal length of the lens and 2a is th: diameter of the circular aperture or the diamete of the lens, whichever is smaller then the linea width of central maximum `=(1.22lamdaf)/(2a)`
`:.` Radius of central maximum,
`r_(0)=(1.22lamdaf)/(2a)=(0.61lamdaf)/(a)`
`:.Deltatheta~~(0.61lamda)/(a)` implying
where `Deltatheta` is the minimum angle required to see the two images just separated.
Here `Deltatheta` is angular resolution of telescope.
An inverse of an angular resolution is called energy resolution or geometric resolution.
Thus, when the diameter of the objective is greater, `Deltatheta` will be smaller. That is for a telescope as a is larger then its power of resolution is higher.
Resolution power : The ability of an optical instrument to produce distinctly separate images of two closely placed object is called its resolving power.