Question
Thu March 05, 2015 By: Ketan G

explain the eye defects and their corrections.
what is the resolving power of the microscope and telescope?
Draw the ray diagrmas for the formation of image in the cases of Compound Microscope, telescope,
and simple Microscope and also write their their magnification powers.
please give the answers in detail.

Expert Reply
Faiza Lambe
Thu March 05, 2015
Resolving power of a microscope:
The resolving power of a microscope is its ability to form separate images of two point objects lying close together. It is determined by the least distance between two point objects which can be distinguished.
This distance is given by,
 begin mathsize 14px style increment straight d equals fraction numerator straight lambda over denominator 2 straight mu space sinθ end fraction
where space straight lambda space is space the space wavelength space of space light space used space to space illuminate space the space object
straight mu space is space the space refractive space index space of space the space medium space between space the space object space and space the space objective. end style
 
The angle begin mathsize 14px style straight theta end style is the half-angle of the cone of light from the point object i.e., it is the angle which a marginal ray makes with the axis of the microscope.
The term begin mathsize 14px style straight mu space sinθ end style is called the numerical aperture of the objective.
The resolving power of the microscope is defined as the reciprocal of the distance between two objects which can be just resolved when seen through the microscope.
begin mathsize 14px style therefore Resolving space power space of space microscope space equals space fraction numerator 1 over denominator increment straight d end fraction equals fraction numerator 2 straight mu space sinθ over denominator straight lambda end fraction end style
The resolving power depends upon:
1. The wavelength  begin mathsize 14px style straight lambda end style of the light
2. The refractive index begin mathsize 14px style straight mu end style of the medium between the object and the objective of the microscope
3. The angle begin mathsize 14px style straight theta end style subtended by the radius of the objective on one of the objects.
 
Resolving power of a telescope:
The resolving power of a telescope is the reciprocal of the smallest angular separation between the distant objects whose images are separated in the telescope.
It is given by,
begin mathsize 14px style dθ equals fraction numerator 1.22 straight lambda over denominator straight alpha end fraction end style
where, begin mathsize 14px style dθ end style is the angle subtended by the point object at the objective
begin mathsize 14px style straight lambda end style is the wavelength of light used
begin mathsize 14px style straight alpha end style is the diameter of the telescope objective
 
A telescope with a larger aperture objective gives a high resolving power.
 
 
Note: Kindly ask the other questions as a separate query.
Fri September 08, 2017

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