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MICROSCOPE WITH GLASS SPHERE

CONTENT


INTRODUCTION

The microscope is an instrument that allows you to visit the very small things, those that inlcuso you cannot see at first and whose existence was unknown until the invention of this. We invited to construct a simple microscope to you that will allow you to investigate in the world of microcosms.

Our microscope is based on one very old one invented by an become fond of scientist of century XVII Anton van Leeuwenhoek call. As its predecessor, our microscope is based on a single but powerful lens.

 

THE LEEUWENHOEK MICROSCOPE

A great part of the scientific discoveries in the past century (and still nowadays) was done by fans. Leeuwenhoek was a simple fabric salesman. It used for his work small “crystal pearls? to examine fabrics in detail. No of the colleagues of Leeuwenhoek had the idea to observe other objects because perhaps they thought that it was not worth the pain to do it. If Leeuwenhoek embargo, had a natural and insatiable curiosity and began to around observe everything his. It examined saliva, blood, static water, vinegar, beer and many other things. All of them were interesting, but the static water (at the most dirty better) was the best object of study. It discovered and it examined many microorganisms. It sent reports to the Academy of Sciences of English, the Real Sociedad of London, that distributed these reports and everybody found out these discoveries

Therefore the founder of the microbiology was a simple fan to science, but the scientific community realized importance of these discoveries only after decades. In order to obtain greater extensions, Leeuwenhoek made small lenses more and more, getting to make lenses of 1 to 2 mm of diameter. These lenses are difficult to hold and to focus and to avoid these Leeuwenhoek problems held them between two bronze plates. It placed what wanted to observe in the end of a screw, so that could regulate in form needs the distance between the object and the lens the observer had to approach the eye the instrument and to look through lens.

This instrument was compound of a single lens. By the great curvature of the lens, this one was very powerful and allowed magnifications of more of 300X almost as much as a modern microscope. This microscope is called “simple microscope?, because it is formed by a single lens. At the same time as Leeuwenhoek, an English physicist called Robert Hooke, had constructed to a compound microscope, that is to say, fact of two lenses: the objective (that go down) and the eyeglass (at where it is looked). Nevertheless the manufacturing techniques of the lenses were not perfect and therefore these microscopes had serious optical defects, which made less cash than the simple microscopes. In first half of century XVIII the compound microscopes were only perfected.

Leeuwenhoek constructed hundreds of microscopes and some of these still exist and they are conserved in museums (fig 1). Essentially, this instrument was not easy to use and it did not have an illumination system.

OUR MICROSCOPE AND THE ONE OF LEEUWENHOEK

In years 50, the Magazine “Scientific American?, D.L. Stong rediscovered the old microscope of Leeuwenhoek and it gave important improvements him. It adapted the use of the portaobjetos and it put a movable mirror to him for the illumination. The most important innovation of Stong is the construction of the lenses. Whereas Leeuwenhoek polished the tiny double convex lenses in form manual, Stong used a simple procedure much more that it was based on the surface tension of the fused glass to obtain very precise spherical lenses. It worked with glass rods and a burner bunsen, with which it obtained very good lenses. Some of the graphs that you will see in this note are of the mentioned North American author.

In the magazine “Scienza & Vita? of December of the ‘93, a microscope done on the basis of the one can be seen of Stong, but with a mechanism different and another type from illumination system.

This microscope can arrive at magnifications from until 200X. What it does very useful in the field, for its use by the Biology professors.

CONSTRUCTION OF THE MICROSCOPE

The microscope that we are going to construct can be divided in four parts:
- The optical part
- Approach equipment
- The structure of support or portaplatina
- The illumination system

So that you have one better idea, you can see figures 1 and 2, if you wish you can make modifications. We already did many, some of which we will tell you soon.

The optical part is formed by the objective lens or. In this case a crystal sphere with a diameter of about 1,2 mm to 2,5 mm that works as a magnifying glass. She is very powerful and it must be maintained to a distance of a few millimeters of the objects that we wished to observe.

AS MAKING THE LENS

In order to make the lens you need (fig.4) a rod glass with a diameter of about 3 mm to 5 mm, a Bunsen burner and a pair of tweezers.

In order to reduce the formation of gas bubbles in the glass spheres, you must wash to the glass rod with water and soap well. It avoids to touch with the hands the central part of the rod. After fitting the flame of the Bunsen burner, warms up the central part of the rod while beams to turn it between the fingers. When the glass is sufficiently hot and soft, acquittal of the flame and hauls with firmness with both hands until obtaining a rod of about 0,3 M. Rompe the rod with the clamp by means, without touching with the fingers. Soon it approaches the flame the thin rod and you will notice that a esferita takes place, leaves it in the flame until it has a size of 1,5 mm to 2 mm Soon removes from it licks and it leaves it sphere cools off. Now it breaks the rod to about 10 mm of the sphere. You will use this colita to stick the sphere in his place. What guarantees the spherical form of the small ball is the surface tension of the fused glass. Although the gravitational force lies down to deform the sphere, to obtain lenses of good quality you must maintain the dimensions that we give you. You will have to prepare some 10 esferitas, soon you examine them with a magnifying glass to choose the one that has the suitable dimensions and that are without air bubbles and other imperfections.
There will be hydrocarbon signs in the glass sphere that you made, reason why you will have to clean it with alcohol and a smooth paper. The power of objective extension of l is greater whichever minor is its size. How you can determine his power of extension? Simply it solves this equation: I=333/d, where I am the extension power and d is the diameter of the sphere expressed in millimeters. For example for a sphere of 1,66 mm of diameter we will have an extension of 200 Xs

APPROACH MECHANISM

As we needed to focus by far care, the lens is subject to a metal lamina connected to two screws. First it serves for the approach and the second for the fine adjustment.
The objective (lens) is placed in one of laminae on a hole. In fig 3 the dimensions are seen. The form in Or gives to two laminae stability him.
As you can see in figures 2 and 3 the base of the objective is curved to give more stability him.

THE PORTAPLATINA

The portaplatina is simply a wood box with two openings to the sides. She is subject with glue and nails. The part of above must have a material as Formic, but it is not very necessary. What yes you must do is a hole of about 10 mm of diameter so that pass the light of the illuminator. Also you must make two holes for the screws.

ILLUMINATION SYSTEM

This is a critical part, because a good illumination will allow us to observe the objects with clearness. The light of the sun does not serve, so he is better to use a small center of lantern.

MOUNTING THE OBJECTIVE

The objective must be stuck under the lamina of approach in the conical seat (fig3).
In order to stick the lens it places a little painting for nails in colita (fig 5). Without touching the lens with the fingers, you must press it a little downwards to eliminate spaces, in fact, if it passes something of light through the edges, the clearness of the image is reduced enough.


USE OF THE MICROSCOPE

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This instrument serves to observe transparent objects. Therefore he is better to choose small objects and I am transparent. You must place the object in a portaobjeto and cover it with a cubreobjeto (fig 6). Ten taken care of when lowering the lens, does not have to get wet nor to be soiled.


It ignites the illuminator, it places to the center the object and places your eye as close as it is possible of the lens. Now it focuses with the screws until the image is seen well (fig 7).

NOTES AND OBSERVATIONS

We could make a much more simple microscope, which will show to them in some days. If embargo these are some of the modifications that we did: the lens you can obtain it from a lamp (or foquito, as tenth in Bolivia) of lantern. You must break everything around so that in the end you have only the lentecito. For illumination we also used a lamp of lantern fed with two batteries and placed underneath the hole where is the lens.



Commentaries or questions? communicate to you with: Miguel Vargas via miguelvargas@originaldustcover.com
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Questions a: Miguel Vargas via info@originaldustcover.com