Site for children


J. Perelman
"Entertaining physics". Book 2.
Chapter 9. Reflection and refraction of light. Vision

WHY MICROSCOPE INCREASES?

"Because it changes the course of rays in a certain way that is described in physics textbooks," that most often hear in response to this question. But in such response shall state the reason; the same essence of the case is not affected. What is the main reason magnifying action of the microscope and telescope?

I learned it not from a textbook, and suffered an accident, when a student once remarked extremely interesting and highly puzzled by me phenomenon. I sat at the closed window and stared at the brick wall of the house in the opposite side of the narrow lane. Suddenly I'm back with dread: with a brick wall - I saw it! - looked at me a giant human eye several meters in width... In that time I have not read the above now the story of Edgar Allan PoE and therefore not immediately realized that gigantic eyes was a reflection of my own reflection, which I designed on the backside of the wall and therefore imagined accordingly increased.

Guessing, what's the matter, I got to thinking about whether it is possible to arrange a microscope based on this illusion. And then, when I failed, it became clear to me, what is the essence of the magnifying action of the microscope: it is not that the subject appears larger size, and that it is viewed at a large angle of view, therefore, it is the most important thing is image takes up more space on the retina of our eyes.


The lens magnifies the image on the retina.

To understand why so essential here the angle of view, we should pay attention to an important feature of our eyes: each item or each part representing us at an angle, the smaller one angular minute, blend for normal sight at the point at which we cannot discern any shapes or parts. When the subject so far removed from the eyes or as well small in itself, that all of it or parts of it are presented at a visual angle of less than 1', we fail to discern in it the details of its structure. Is it because at this angle of view image of the object at the bottom of the eye (or image of any part of the subject) captures not many nerve endings in the retina immediately, and can fit on a single sensitive element: details of form and structure then disappear, we see the point.

The role of the microscope and the telescope is that, changing the course of the rays from a given object, they show it to us at a large angle of view; the image on the retina is stretched, captures more nerve endings, and we distinguish already subject to such details that were previously merged. "The microscope or the telescope increases 100 times," it means that he shows us the subject from the perspective of 100 times more than we see them without tools. If an optical instrument does not increase the angle of view, it will not give any increase, at least to us and it seemed that we see the subject increased. Eyes on the brick wall seemed huge, but I did not see him any extra detail compared to what I see, looking in the mirror. The moon low on the horizon seems to be significantly greater than high in the sky, " but is this increased drive we notice one extra spot, indistinguishable at high standing Magnifier?

If you refer to the occasion of the increase described in the story of Edgar Allan PoE "the Sphinx", we make sure that a larger facility was not provided any new particulars. The angle remained unchanged, the butterfly is seen under the same angle, consider whether we are far away in the forest or close to the frame of the window. And time does not change the angle of view, the increase in the subject, no matter how impressed he is your imagination, not open to the observer no new details. As a true artist, Edgar According to the true nature and even at this point of his story. Did you notice how he describes the beast in the forest: the list of individual members of the insect does not enter into any new features compared with what is "dead head" when observed with the naked eye. Compare both descriptions, they are not without intent described in the story, and you will see that they differ only in verbal expressions (10-foot plate - scales, giant horn - antennae; boar's tusks - tentacles, and so on), but no new details, indistinguishable to the naked eye in the first description no.

If the action of the microscope was only at this magnification, it would be useless to science, becoming curious toy, nothing more. But we know that this is not the case that the microscope has opened a new world to a person, far-extending the boundaries of our natural vision:

Even the sharp eyes of our nature,
But near the end thereof has power.
Kohl lot of things but he still dosages,
Which small rise before us sokrawaet!

wrote our first naturalist Lomonosov in the Letter about the benefits of glass". But in current centuries we the microscope revealed the structure of the smallest, invisible beings.

Kohl thin members in them, compositions, heart, veins
And nerves that are stored in a brute force!
Not less than in the depths of the grave kit.
Us small worm parts by adding divit...
Kohl lot microscope we secrecy opened
Invisible particles and thin in the body lived!

Now we can give a clear account of the fact why the microscope reveals to us the "confidentiality", which is not provided on your monster-butterfly observer in the story of Edgar Allan PoE: because - let us summarize the above - microscope is not just present objects in a larger view, and shows them at a large angle of view; as a consequence, on the back of the eye is drawn enlarged image of the object acting on the more numerous nerve endings and those delivering our consciousness a greater number of individual visual impressions. In short: the microscope increases are not objects and their images are at the bottom of the eye.

Entertaining physics J. Perelman

 




System Orphus

SUPPORT THE SITE!

Did you like our site and you would like to support it? It's very simple: tell your friends about us!
Read MORE

  © 2014 All children