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AS and A Level: Microscopes & Lenses

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  • Peer Reviewed essays 16
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  1. Peer reviewed

    The advantages and limitations of electron microscopy.

    4 star(s)

    As biologists came to realise these limitations they understood that the only solution was to find a way of employing a shorter wavelength. The electro-magnetic spectrum shows us that either ultraviolet light or X rays could be used. Both were tried, but neither proved to be satisfactory. It became apparent that a more effective solution would be to use electrons. Electrons are negatively charged particles that form an orbit around the nucleus of an atom. Electrons can break form this orbit when the atoms are heated to very high temperatures.

    • Word count: 1308
  2. Peer reviewed

    Ray tracing

    4 star(s)

    We found that if the lens is thin, the focal length is longer, and if it is thicker, the focal length is smaller. The focal length for our lens is 10cm. I have created some ray tracing diagrams to show my predicted lengths using the focal length that I found. I have found the longest distance that I can get a clear image is 100cm, the shortest being 15cm.

    • Word count: 635
  3. Peer reviewed

    Microscopy. History of the microscope:-

    3 star(s)

    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. Leeuwenhoek's microscope * 1872 - Ernst Abbe wrote a mathematical formula - "Abbe Sine Condition". His formula provided calculations that allowed for the maximum resolution in microscopes possible. * 1903 - Richard Zsigmondy developed the ultra microscope that could study objects below the wavelength of light. * 1932 - Frits Zernike invented the phase-contrast microscope that allowed for the study of colourless and transparent biological materials * 1931 - Ernst Ruska co-invented the electron microscope.

    • Word count: 1498
  4. Peer reviewed

    Electron microscopes allow the viewer to see much smaller objects than the original light microscopes. The wavelength of electrons is thousands of times smaller than the wavelength of light

    3 star(s)

    As electrons cannot be seen as light can, the image is shown on a screen when the electrons are detected within the microscope. A stream of electrons is formed at a hot cathode, or 'electron gun' inside the microscope, which is then 'fired' at the object being viewed using positive electrical charges. Metal apertures and magnetic lenses are used to confine the stream into a thinner, more focused beam. The beam is then directed onto the sample by magnetic lenses.

    • Word count: 509
  5. Peer reviewed

    What Are the Advantages and Disadvantages of A Light And Electron Microscope?

    3 star(s)

    When I stained a specimen on my slide for microscopy, I saw the colours which were very vivid. They are also easier to use. Also it is comparatively cheaper than the second microscope up for discussion- the electron microscope. As the light microscope was made very early on, as mentioned once before, it does have a lot of limitations due to that age. The only and maybe the most significant problem is its inability to show the finer details of any specimen. The light microscope obviously uses light and a type of refraction of it, to show the magnified specimen. However no matter hoe much you magnify the sample it does not increase in the level of detail.

    • Word count: 875
  6. Peer reviewed

    An Essay about Microscopes

    3 star(s)

    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 bacteria, yeast, blood cells and many tiny animals swimming about in a drop of water.

    • Word count: 920
  7. Peer reviewed

    A comparison between light microscopes with electron microscopes

    3 star(s)

    One man, however, is generally credited with bringing the microscope to the attention of biologists. Anton van Leeuwenhoek. His home made microscopes were very small simple instruments with a single very strong lens. Though awkward to use, they enabled seeing highly detailed images. Due to the limitations of light microscopes, electron microscopes were developed. In the 1930s, biologists found that light microscopes had theoretical limits, and the scientific desires to see fine details of the interior structures of organic cells were increasing. The first type of electron microscope to be developed was the transmission electron microscope and includes a focused beam of electrons to see through the specimen.

    • Word count: 833
  8. Peer reviewed

    Comparing the Light and Electron Microscope

    3 star(s)

    For the light microscope this distance is approximately 0.2�m. 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 the wavelength of visible light, and means that little is gained by magnifying an object more than 1500 times.

    • Word count: 1054
  9. Peer reviewed

    Describe the principles and limitations of transmission and scanning electron microscopes. Specific reference should be made to magnification and resolution

    3 star(s)

    Principles and Limitations of light microscopy Light microscopes function by focussing a beam of light on the object to be examined.The beam passes through a series of lenses after passing through the specimen.The condenser lens focuses the light onto the specimen for maximum illumination.The lower objective lens magnifies the object ,and the image from this lens is further enlarged when viewed through the upper eyepiece lens.The beam from the light source directly enters the observer's eye.It has a few limitations.Material to be examined by light microscopy must be sufficiently transparent and thin enough for light to pass through .They are

    • Word count: 1040
  10. Peer reviewed

    The Principles and Limitations of Electron Microscopy.

    3 star(s)

    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 feature and materials properties, e.g, hardness, reflectivity...etc. Morphology: The shape and size of the particles making up the object; direct relation between these structures and materials properties e.g, ductility, strength, reactivity...etc.

    • Word count: 1160
  11. Peer reviewed

    Electron microscopes.

    3 star(s)

    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 just that in this case electron beams are used instead of light beams. With this type of electron microscope the beam of electrons is passed through the specimen before being viewed. Only the electrons transmitted (That is the electrons that go through the specimen)

    • Word count: 919
  12. Peer reviewed

    The Use and Operation of the Light and Electron Microscope

    3 star(s)

    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 used as these refract the light, and although the image is inversed, the image is much larger, as is illustrated below. Electron microscopes There are two main types of Electron Microscope, the first is a transmission electron microscope (TEM)

    • Word count: 1136
  13. My experiments focus is to obtain an accurate measurement for a specific lenss power.

    An image is formed at this point (in my case the filament of the lamp/when LED is most intense). * Lens holder: This is a vital piece of apparatus as it keeps the lens firmly in position. I placed this on top of a wooden block so the lens axis was at the same height as the centre of the light source, allowing an image to be formed. * Screen: This was simply a thin wooden block with white paper on the front of it. It is beneficial that the paper is white as it reflects most of the light cast on it.

    • Word count: 5969
  14. Aim: to find the refractive index of water

    The gradient shows the experimental value of the refractive index of water is 1.20+-0.26. The systematic error could be the thickness of the mirror. Then, the position of the virtual image in the water will appear to be higher then the actual one. This will affect the apparent depth and thus the refractive. The other systematic error is the bulge of the middle part of water compared to area all around. Like the first one, this could also influence in the measurement of the apparent depth.

    • Word count: 851
  15. Use of the material Zerodur in the KECK observatory telescope. The very low CTE makes ZERODUR ideal for use as part of the primary mirror. This means that over the temperature range that is possible that the telescope works in, (0-50C), the materi

    This meant that the primary mirror would be made from smaller sections, allowing easier maintenance, installation and construction. The mirror is made of 36 hexagonal sections, and forms a slight curve, as shown in figure 1. Fig 1. - A diagrammatical representation of the 36 segment mirror. The black hexagon in the middle represents a gap; placing a mirror here would be pointless as the light that would hit this part of the mirror is obscured by the secondary mirror, which is attached straight above this, and collects the light reflected by the other primary mirror1.

    • Word count: 2300
  16. Free essay

    Formation of Lens

    A person who is suffering from this disease only see objects that is near to the eye clearly. This means you cannot see objects at a distance which appeared to be blurred. If the eye has myopia the eye is too long and the image falls short of the retina when the target object is far away. The image shows that in myopia the image fall short of the retina when the target object is far away. CONCAVE LENS FOR NEARSIGHTEDNESS A concave lens is a diverging lens which works similar to the convex mirror.

    • Word count: 602
  17. Measuring the focal length of a lens for red and green light- Case Study

    Once this happens the optical nerve sends messages to the brain and it is the brain that actually converts this to an image for us to see. The lens of an eye works in a similar way to a converging lens. A converging lens refracts light that passes through it to a single point; this is known as the focal point. The diagram below shows some information on the focal point and focal length: Eye defects: The eye above shows an eye that has no problems with it.

    • Word count: 1252
  18. Measurement of the focal lengths of a concave lens and a convex mirror

    Calculate the focal length of the concave lens f by using the lens formula: By using real-is-positive convention, u will be taken as negative. Measurement of the focal length of a convex mirrorusing an auxiliary convex lens 1. Position the screen to catch the real image formed by the auxiliary convex lens 2. Add the convex mirror between the screen and the convex lens and move it to and fro until an image I forms coincide with the object O.

    • Word count: 1050
  19. An investigation into the workings of the opticians

    Light that hits the rest of the macula will be slightly less clear but will still be in focus The 'rods and cones' spoken of are actually two different types of photo receptor. The 'cones' are primarily adapted to detect colour so function well in bright light whereas the 'rods' are more sensitive but are not as proficient in detecting colour due to the fact that they are adapted to dim light. In the average human the ratio of rods to cones is approximately 120:6 million cells.

    • Word count: 1394
  20. Refraction of Light Lab Report

    Materials: - ray box - plexiglass - white paper, protractor and pencil Procedure: 1. I folded the blank paper into four equal parts. Then drew two intersecting lines perpendicular to each other. 2. Using the protractor I drew the angles of incidences or rays measuring 10�, 20�, 30�, 40�, 50� and 60�. 3. Then I drew a semi-circle on the top of the intersection representing the flexi glass and placed the flexi glass over the semi-circle. 4. Plugged in the ray box to a power source and using the single slit barrier, I placed the light ray along the normal to ensure that the light is not bent at this point.

    • Word count: 922
  21. Does the focal length of a lens depend on the colour of light used?

    Throughout my coursework U will stand for ...... and V will stand for.......... Apparatus 1) Ray box (12V) 2) Power supply (able to supply12V) 3) Object slide 4) Lens of unknown focal length 5) Lens holder 6) Screen 7) Screen holder 8) Meter rule 9) 30cm ruler 10) Light blocking slides x 3 Working out appropriate Object distances On my graph I want at least 8 points to make sure that the line made is as accurate as possible. And I worked out the rough focal length by using my lens by producing an image of the trees outside the classroom on the wall, and found this to be around 19cm.

    • Word count: 2626
  22. Observatory Visit

    The South Kensington site was being cleared to make space for the Science Museum and extensions to the Royal College of Science, now Imperial College. A spectrum of a star is composed of a number of 'lines' which can be either emission or absorption lines. The continuum emission is a product of the blackbody radiation at specific frequencies, caused by electrons in atoms dropping down into lower energy levels. They can also be caused by molecular transitions to lower energy levels.

    • Word count: 908
  23. Lenses experiment

    Variables My independent variable will be moving the object. My dependant variable will be the lens. There are two common types of lenses convex (converging) lenses and concave (diverging) lenses. As you can see by looking at these diagrams a convex lens can make a real or a virtual image and a concave lens can only make a virtual image. I am using a convex lens in this experiment so that I can measure the size if the image and to be able to do that my image needs to be real, but only a convex lens produces a real image.

    • Word count: 3668
  24. aspects of physics

    and change them; another reason is that if the lights were directly above the pool then condensation would cause the lights to break. This helps to spot any foreign object in the pool, as if there was a dark pool they not be spotted and if there was someone under water drowning it would make it harder for the lifeguard to spot them the less light there is. Also simply to help people to see when they are swimming on the surface or underwater as the more light there is it makes it clearer to see.

    • Word count: 1899
  25. This essay is on vision, its malfunctions & diagnostics methods.

    These are Myopia (nearsightedness), Hyperopia (farsightedness) and Astigmatism (inappropriate path of light rays to the eye). Myopia and hyperopia are termed spherical disorders as both can be corrected with spherical lens. Astigmatism on the other hand is an aspherical disorder as it is corrected with cylindrical lenses1. Myopia influences the ability to see distant objects, in which the object is perceived as blurry. This is because the object is not focused directly on the retina, but in front of it.

    • Word count: 2173

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