The history, development and use of the light and electron microscope
The history, development and use of the light and electron microscope History of light microscope Observing objects in detail greater than the naked eye was very interesting to people at early stage. This led to the construction, in the 16th century, of a magnifier composed of a single convex lens, and this, in turn, led to the eventual development of the microscope. The most famous early pioneers in the history of the microscope are Digges of England and Hans and Zcharias Janssen of Holland. But it was Antony van Leeuwenhoek who became the first man to make and use a real microscope. Leeuwenhoek ground and polished a small glass ball into a lens with a magnification of 270X, and used this lens to make the world's first optical microscope. Because it had only one lens, Leeuwenhoek's microscope is now referred to as a single-lens microscope. Its convex glass lens was attached to a metal holder and was focused using screws. The light microscope system was invented in the seventeenth century. This type of microscope incorporates more than one lens so that the image magnified by one lens can be further magnified by another. Today, the term "microscope" is generally used to refer to this type of compound microscope. Since its invention, the light microscope has made tremendous progress and help figure out many biological molecules. Using a light microscope that he had
Physics coursework; Finding the focal length of a lens using a graphical method.
Physics coursework; Finding the focal length of a lens using a graphical method. Planning: Firstly the rough focal length of my lens will need to be found to assist me in my real experiment. A simple way to do this would be, to hold the lens up to a flat white wall opposite a window when it is light outside, by moving the lens closer/ further away from the wall until an upside down image of objects outside the window (e.g. trees,) is produced, I can estimate an focal length for the lens which provides me with the minimum distance of (u), this saves time that would be spent trying to find a point from which I can begin measurements. The equipment will be set up as shown below: Apparatus: * Light source connected to a power pack * Wire grid (object) * 1m ruler (correct to the nearest mm) * a small bi-convex lens * a white 2D screen (approx 100*70 mm) ==> When the light is turned on the light will pass through the mesh creating an image which can be focused by the lens on the screen. ==> It is important to remember that light bulbs will get hot, so precautions should be taken to ensure I am safe from burns during the experiment. ==> It should also be considered that any experiment involving electricity carries risk so due care must be taken when handling any electrical equipment. ==> The light source will be covered with a sheet of grease proof paper, this will
Microscopy. History of the microscope:-
Microscopy Microscopes are tools which allow us to see objects which we cannot see with the naked eye. There are two main types of microscopes used nowadays. These are light microscopes and electron microscopes. During the 16th century the microscope was invented, which was of great assistance to works in medicine and biology. At first, the microscope was basically used recreationally, and was found in the homes of wealthy people. However, not long afterwards, proper uses for the microscope were discovered, and so study of bacteria and diseases began. History of the microscope:- * Circa 1000AD - First vision aid was invented called a reading stone. It was a glass sphere that magnified when laid on top of reading materials. * Circa 1284 - Italian, Salvino D'Armate invented the first wearable eye glasses. * 1590 - Zaccharias Janssen and his son Hans Janssen experimented with multiple lenses in a tube and observed that objects appeared greatly enlarged * 1665 - Robert Hooke noticed some "pores" or "cells" in a sliver of cork looking through a microscope. * 1674 - Anton van Leeuwenhoek built a simple microscope with only one lens to examine blood, yeast, insects and other tiny objects. He invented new methods for grinding and polishing microscope lenses that allowed for curvatures providing magnifications of up to 270 diameters, the best available lenses at that time.
The advantages and limitations of electron microscopy.
The advantages and limitations of electron microscopy There are two main branches of microscopy that are pertinent to cell biology. These branches arise from the two types of microscope; the light microscope and the electron microscope. The basic principles of light microscopy have been known since circa 17th century, however improvements in lens manufacture in circa 19th century allowed the use of microscopy to be much more practically available and useful. This is increased ability inspired rapid research into both the design of microscopes and the preparation of specimens. However, the light microscope can only magnify objects bigger than 0.2 micrometres; due to its limited resolving powers. This is because it utilises a beam of light. Relatively, light has a long wavelength, this means that when there are two small points close together there is too much refraction and wave front overlap, the eye then only sees one point. This can also be considered in terms of objects "crossing the path" of the wavelength. The smallest wavelength of visible light is 400nm, the diameter of mitochondria is 1000nm, and therefore mitochondria cross the path of the light wave. However ribosomes have a diameter of 22nm, and do not cross the path of the light wave and are therefore not seen by the light microscope. As biologists came to realise these limitations they understood that the
The Principles and Limitations of Electron Microscopy.
The Principles and Limitations of Electron Microscopy. An Electron Microscope is a type of microscope that makes use of a beam of electrons rather than visible light. Which is due to the fact that the wavelength of electrons is much smaller than the wavelength of visible light, an Electron Microscope not only gives a high magnification but it also has high resolution. This means that details can be seen clearly. An Electron Microscope is very similar to a Light Microscope in the ways in which it works but, instead of using glass lenses to focus a beam of light, it uses magnets to focus a beam of electrons. Electrons are very small, so they are scattered if they hit molecules in the air due to this they must travel through a vacuum. Specimens that are to be examined must be cut into very thin sections, and these must be treated so that they can be examined in these conditions. The variety of chemical processes that are carried out in this preparation may change the appearance considerably. Features which have been introduced in this way are known as artefacts and care needs to be taken in interpreting electron micrographs because of the possible presence of artefacts. An examination of a specimen using an Electron Microscope can yield the following information: Topography: The surface features of an object or "how it looks", it's texture; direct relation between these
The Use and Operation of the Light and Electron Microscope
The Use and Operation of the Light and Electron Microscope Light microscopes were first used in the seventeenth century, famously by the scientist Robert Hooke; the man that first named 'cells'. It was not until the nineteenth century however that microscopy became popular. Before this time, the lenses had not been of high enough quality to view images clearly, in the early nineteenth century improvements were made and the identification of cell structures began. Problems with resolution then became apparent; a wave length shorter than light needed to be used in order to improve the clarity of image produced; Electron microscopes were developed as a solution; both Ultraviolet light and X-rays have shorter wave lengths but it was found that these were extremely difficult to focus. Electrons, however, are negatively charged particles; this gives the advantage of being able to focus them easily, by use of electromagnets. These electromagnets act in exactly the same way as a lens would on a Light Microscope. How light microscopes work In a compound light microscope; a light source is located underneath the stage. The light goes through a condenser lens and through the specimen, the resulting light is then passed through two more lenses, both used to magnify the image and focus towards the ocular. The lenses used indicate the resulting magnification of the specimen. Lenses are
Comparing the Light and Electron Microscope
Comparing the Light and Electron Microscope In this essay I am going to be comparing the light and electron microscope, I will look at the advantages and disadvantages of each microscope and then analyse my findings to see if one is better than the other. The light, or optical microscope as it is also known was invented in the 17th century, it has been refined in many ways over the years but it is essentially still the same. The light microscope works by; light rays from a light source beneath the stage are through to glass lenses in series. The two lenses are called the objective lens and the ocular (eyepiece) lens. Depending on their strength these two lenses on their own routinely provide magnifications of up to 400 times. There is a limit to the amount of detail the light microscope can show, this limit is set by the resolving power. The resolving power is the minimum distance by which two points must be separated in order for them to be perceived as two separate points, rather than a single fused image. For the light microscope this distance is approximately 0.2µm. So in theory it might seem possible to magnify an object indefinitely by means of glass lenses in series. This has been put into practice and has only produced a larger and fuzzier picture; so the resolution is not improved and no more detail is visible. The resolution of the light microscope is imposed by
Describe the principles and limitations of transmission and scanning electron microscopes. Specific reference should be made to magnification and resolution
Describe the principles and limitations of transmission and scanning electron microscopes.Specific reference should be made to magnification and resolution Introduction Microscopy has a major role in cytology.From the very beginning researchers have tried to develop ways of looking directly at living cells.This examination has revealed much about the morphology of cells and tissues.In recent years,development in microscopes,dyes,staining and preparatory techniques have helped reveal even more about the structure and function of cells.Microscopes have a certain magnification and resolving power.In any microscope the the resolving power is more important than the magnification.The resolving power of a microscope is the least distance between two objects where the microscope can still distinguish the objects as being separate.It is a measure of detail that can be seen.A microscope with a high resolving power enables us to view images with a high resolution.With a low resolution they would be viewed as one object.Microscopes with a high magnification are only able to increase the size of the object that is being viewed.The resolution will be the same.(ie the object will still lack clarity and appear fuzzy).The two types of microscopes are electron and light microscopes. Principles and Limitations of light microscopy Light microscopes function by focussing a beam of light on
An Essay about Microscopes
Microscopes The word Microscope it given to the tool used to view object that are too small to be seen with the naked eye. During the 1st century AD, glass had been invented and the Romans were looking through the glass. They experimented with different shapes of clear glass and one of their samples was thick in the middle and thin on the edges. They discovered that if you held one of these pieces of glass over an object, the object would look larger. Before microscopes as we know where invented, what was considered as a microscope was just really a Magnifying Lens, early biologist used them to study tiny insects such as Fleas, thus the viewer was called a Flea Lens. Two Dutch spectacle makers in the 1590's (Zaccharias Janssen and his father Hans) experimented with lenses and realised that if several lenses were put into a tube and the object is viewed it appears larger than viewed by any magnifying lens, this was the invention of the Compound Microscope. Anthony Leeuwenhoek of Holland who worked in a dry goods store had a great interest in lens and began making some of his own. By grinding and polishing, he was able to make small lenses with great curves. His rounder lenses produced greater magnification. Anthony Leeuwenhoek's new microscope got him interested in science and with his new improved microscope was able to see things that no man had ever seen before. He saw
Electron microscopes.
ELECTRON MICROSCOPY This is the act of using electron microscopes. Electron Microscopes are scientific instruments that use a beam of highly energetic electrons to examine objects on a very fine scale. Electron microscopes can be used to view the topography (surface), the morphology (the shape and size of the particles making up the object) and also the composition (elements and compounds the object is composed of and how many: in case of cell organelles). Electron microscopes were introduced or developed due to the limitation of light microscopes. This is because the resolving power of a microscope depends on the wavelength of the electromagnetic radiation used; because the light microscope uses only the visible part (light) of the electromagnetic spectrum whose shortest wavelength is 400 nanometre (violet light), therefore objects smaller than half of the wavelength (200nm) cannot be viewed using a light microscope. E.g. cell organelle ribosome is 20nm and can never be seen using a light microscope. As electron microscopes uses electrons, which are negatively charged and beams of electrons have a very short wavelength. This type of microscope has a very high magnification and resolution power. They are two major types of electron microscopes the first type originally developed: The Transmission Electron Microscope, which is quite similar to the light electron microscope