Question

What is the advantage of a compound microscope over a simple microscope?

Answer 1

Hint: We have to explain how compound microscopes produce highly magnified images of an object. In addition to this, they are easy to use and simple to store. Compound microscope comes with its own light source.

Formula used:
For simple microscope, $M=1+\dfrac{D}{F}$

For compound microscope, $M={{m}_{e}}\times {{m}_{o}}$

Complete step by step answer:
A simple microscope is the one that uses a single lens for magnification, such as a magnifying glass. It has a double convex lens with a short focal length. When an object is kept near a simple microscope, the image produced is erect and bigger in size than the object itself. The image formed by a simple microscope is virtual and cannot be obtained on a screen.

Magnifying power of a simple microscope is given by,

$M=1+\dfrac{D}{F}$

Where,

$D$ is the least distance of the distinct vision and $F$ is the focal length of the convex lens.
A compound microscope uses multiple lenses for magnification. They contain two sets of lenses: the Ocular lens in the eye-piece and the Objective lens kept close to the sample. Compound microscopes are used to observe the samples at high magnification.

Magnifying power of a compound microscope is given by,
$M={{m}_{e}}\times {{m}_{o}}$

Where, ${{m}_{e}}$ and ${{m}_{o}}$ are the individual magnifying powers of the eye-piece and the objective lens respectively.

Compound microscope consists of two optical components: the objective lens, having a very short focal length and placed close to the object; and the ocular or eye-piece system having larger focal length which further magnifies the image and projects it on the screen as a real image. The objective and ocular lens acts in series, therefore, the total magnification in a compound microscope is a function of the objective lens magnification multiplied by the eye-piece magnification.

The advantages of using compound microscope over a simple microscope are:

(i) High magnification is achieved, since it uses two lenses instead of one.
(ii) It comes with its own light source.
(iii) It is relatively small in size; easy to use and simple to handle.
(iv) Limitations on resolution by simple microscopes can be resolved by using compound microscopes.

Note: Students should not get confused between the size of focal length and the magnification produced by the lens. The shorter the focal length, larger will be magnifying power. Since a compound microscope has an objective lens with short focal length, it gives a higher value of magnifying power as compared to a simple microscope.