Resolving Power of Telescope and Microscope - A Complete Guide

What is Resolving Power?

Resolving Power is the ability of an optical instrument (like a microscope or telescope) to clearly show two close objects as separate.

What is the resolving power of a microscope and telescope?

Resolving Power of a Microscope

The resolving power of a microscope is its ability to distinguish two very close points on a small object as separate. It depends on the wavelength of light ( $\lambda$ ) and the numerical aperture (NA) of the microscope lens.

$
\text { Resolving Power of Microscope }=\frac{1}{d}=\frac{2 n \sin \theta}{\lambda}
$

Here,

• $d=$ minimum distance between two points that can be seen separately
• $n=$ refractive index of the medium between object and objective lens
• $\theta=$ half-angle of the cone of light entering the objective lens

Resolving Power of a Telescope

The resolving power of a telescope is its ability to distinguish two distant stars (or objects) that appear very close together in the sky.

$
\text { Resolving Power of Telescope }=\frac{1}{\theta}=\frac{D}{1.22 \lambda}
$

Here,

• $\theta=$ smallest angular separation between two objects
• $D=$ diameter of the telescope's objective lens
• $\lambda=$ wavelength of light used

Difference between Telescope and microscope

• A Telescope is an optical instrument which let us see object up close which is at distant from it like Planets , Stars etc. while
• A microscope is an optical instrument which also allows seeing objects up close but with detailed magnification. This instrument is used mainly to enlarge and magnify smaller objects like microorganisms , cells, study of plants etc.

What is a Microscope?

A microscope is an optical instrument used to see tiny objects that cannot be seen clearly with the naked eye. It works by magnifying the image of small objects, such as cells, bacteria, or fine details of materials. A microscope uses one or more lenses to bend (refract) light and enlarge the image. The most common types are the simple microscope (one lens) and the compound microscope (two or more lenses).

Example: Used in laboratories to study microorganisms, tissues, and cells.

What is a Telescope?

A telescope is an optical instrument used to see distant objects by collecting and focusing light or other forms of electromagnetic radiation. It helps us observe stars, planets, and galaxies that are far away from Earth. Telescopes can be refracting (use lenses) or reflecting (use mirrors).

Example: Used in astronomy to study celestial bodies like the Moon and planets.

Resolving Power of Grating:

The resolving power of a diffraction grating is its ability to separate two very close wavelengths of light. It depends on the number of lines ( N ) and the order of diffraction ( n ).

$
R=n N
$
A grating with more lines gives better separation of light, which means higher resolving power.

Limit of Resolution:

The limit of resolution is the smallest distance between two points or objects that can still be seen as separate. If the objects are closer than this limit, they appear as one. It depends on the wavelength of light and the aperture of the instrument.

Resolving Power of Human Eye:

The resolving power of the human eye is the ability to distinguish two close objects as separate. Under normal conditions, the minimum angle the eye can resolve is about 1 minute of $\operatorname{arc}\left(1 / 60^{\circ}\right)$. This is why we can see distant objects clearly but cannot separate very tiny details without instruments.

Also check-

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NCERT Physics Notes:

• NCERT Notes Class 11th Physics
• NCERT Notes Class 12th Physics
• NCERT Notes For All Subjects