Resolving Power

The ability of an optical instrument to produce distinctly separate images of two objects very close to each other is called the resolving power of the instrument.

The minimum distance of separation between two objects when they can be observed as separate by an optical instrument is called the limit of resolution of that instrument.

The reciprocal of the limit of resolution is called its resolving power.

The reciprocal of the least angular separation between the objects that are just resolved is called the resolving power of the telescope.

The quantity μ sin ⁡θ, where μμ is the refractive index of the medium between the object and the objective, is called the numerical aperture (N.A.) of the objective of the microscope.

R.P. = \[\frac {1}{\text {Limit of resolution}}\]

R.P. = \[\frac {1}{d}\] = \[\frac{2\mu\sin\theta}{\lambda}\]

where μ sin⁡ θ is the Numerical Aperture (N.A.) of the objective.

R.P. = \[\frac{1}{d\theta}=\frac{D}{1.22\lambda}\]