The microscope is one of the most important inventions of all times. Before it has been constructed our idea about the world was limited to what we could see with a naked eye. The microscope created new perspective to study the (micro and macro) universe.
Do you need a lot of money to demonstrate the scheme and principles of operation of a microscope?
Try to build a microscope cheaply. You will need a magnifying glass and a small glass ball. Keep the ball immediately above the object under observation and place the magnifying glass at a distance of 20 cm from the ball. You can observe a magnified image through this optical system.
A real microscope, as well as this toy, consists of a long tube at the end of which an eyepiece (ocular) and an objective, both being convex lenses, are fixed.
The objective collects the light radiating (or reflected) from the specimen and creates its enlarged (real) image, whereas the eyepiece, close to the eye, enlarges this image further.
The first microscopes had thick spherical lenses. Their constructor, Anton van Leeuwenhoek went down in history as the originator of microbiology, by sheer coincidence. He traded in baize and spices, and one day he decided to find out why pepper has sharp (peppery) flavour. He suspected, that the seeds had minuscule hooks, by means of which they stuck to the tongue. He ground some seeds and poured water over them, to make them soft. Since he was very busy, he inspected the seeds only after a few days: they were teeming with microbes.
The diagram shows the optical path of light beams in a microscope. The image viewed in an eyepiece is a virtual image and it is highly enlarged. The angular multiplication of an optic microscope is described by the following equation:
w = (x × D)/(fob × fok),
in which x - stands for the length of a body tube, D - is the viewing distance (250 mm), fob and fok are an objective and an eyepiece focal length respectively. The actual magnification is the product of the powers of the eyepiece and the objective lens being used. In practice microscopes with the power from several dozen to 1000 are applied.
