Light Microscopes - Setting up a light microscope and preparing a temporary slide.

Light Microscopes - Setting up a light microscope and preparing a temporary slide. Introduction Microscopes are essentially used in science labs, industries and schools etc. They are used to magnify small objects and make them visible to show details of their structure. There are two main types of microscopes; a light microscope and an electron microscope. Many living cells can be observed using a light microscope by preparing a temporary slide. Safety points * Be cautious when handling glass slides and cover slips. * Always clean slides and microscopes when finished. Materials used: Microscope Microscope slide Onion Cover slip Pipette Mounted needle Iodine solution Filter paper Method - Setting up a light microscope ) The microscope was checked that it was on low power. 2) The microscope slide was secured on the stage with the object inline with the centre of the stage. 3) The coarse focus knob was turned so that the objective was as close to the microscope slide as possible. 4) The slide was focused away until the object was in focus. 5) The revolving turret head was turned until the high power objective (x40) was in line with the stage. 6) Using the fine focusing knob, the image was focused until the object was sharp. Method - Preparing a temporary slide ) An onion bulb was cut through vertically and one of the leaves of the bulb was separated

  • Word count: 610
  • Level: AS and A Level
  • Subject: Science
Access this essay

Microscopes.101605

The most widely used microscopes are optical microscopes, which use visible light to create a magnified image of an object. The simplest form of optical microscope is the double-convex lens with a short focal length. These lenses can magnify an object by up to 15 times. In general, however, a compound microscope is used, which has multiple lenses to provide more magnification than a single convex lens could alone. Some optical microscopes can magnify an object by 2,000 times or more. The compound microscope consists essentially of two lens systems, the objective and the ocular, mounted at opposite ends of a closed tube. The objective lens is composed of several lens elements that form an enlarged real image of the object being examined. The microscope lenses are set up so that the real image formed by the objective lies at the focal point of the ocular; the observer looking through the ocular sees an enlarged virtual image of the real image. The total magnification of the microscope is determined by the focal lengths of the two lens systems. The accessory equipment of an optical microscope includes a firm stand with a flat stage for holding the material to be examined, and some means for moving the microscope tube towards and away from the stage so that the specimen can be brought into focus. Ordinarily, specimens for microscopic examination are transparent and are viewed by

  • Word count: 1546
  • Level: AS and A Level
  • Subject: Science
Access this essay

I intend to show how the position and nature of the image can be worked out using ray diagrams - I will use various formulas to aid me in figuring out the focal lengths.

Physics SC1 ]For my experiment I am going to try and find out how the position of a lens affects the image for a convex lens. I intend to show how the position and nature of the image can be worked out using ray diagrams. I will use various formulas to aid me in figuring out the focal lengths. In my preliminary work I figured out that the focal length of my lens is 10cm. I did this by simply placing the lens and a screen in front of a window and moving the screen back and forth until the image of the window appeared focused (the edges were sharp and definitive) on the screen and then measuring the distance of the screen from the lens. Background Information There are two different types of lens, convex and concave lenses. Convex lenses are thicker in the middle than they are on the outside whereas concave lenses are thicker on the outside than in the middle. Light rays passing through a concave or diverging lens are bent away from the principal axis of the lens (the line passing through the center of the lens, or optical center, at right angles to the lens). Light rays passing through a convex or converging lens are bent towards the principal axis. When light rays have passed through a convex lens they eventually meet (unless there are special circumstances which will be mentioned later on) the point where they meet is called the principal focus (F). The distance of F

  • Word count: 1234
  • Level: AS and A Level
  • Subject: Science
Access this essay

Explain how the electron microscope has affected our knowledge of cell form and structure

Wednesday 9th October 2002. Explain how the electron microscope has affected our knowledge of cell form and structure. Electron microscopes use a beam of electrons instead of light to produce images of specimens. There are two types of electron microscope: - Transmission electron microscope Scanning electron microscope How an electron microscope works. Electrons are generated in an electron gun, which applies a high voltage of about 100,000 volts through a filament called a tungsten filament. The filament is heated to above 3000 degrees Kelvin, which is roughly 3273 degrees Celsius. Applying an increasing negative voltage to a cathode assembly, which is located just above an anode plate, accelerates the electrons. The anode plate has a tiny hole in its centre, the electron beam is sent through this hole creating a very concentrated beam of electrons. This beam is focused using magnetic coils that act like the condenser lenses that you find on a light microscope. The specimen is on a plate just above a second magnetic coil, which acts as an objective lens. The objective lens resolves the structure and magnifies it slightly. Focusing the specimen can be achieved by altering the electric current through the lens. More magnetic coils act as projector lenses, which enlarge the image. All specimens in electron microscopy are placed in a vacuum, this means that all

  • Word count: 1107
  • Level: AS and A Level
  • Subject: Science
Access this essay

The eye.

The adult eyeball is about 2.5 cm in diameter. The eyeball is held in place by six extrinsic muscles, which allow the eye to be moved. The front surface of the eye is protected by the eyelids and the eyelashes. The reflex action of 'blinking' protects the surface of the eye. Under the eyelids is a thin transparent layer called the conjunctiva. This is kept moist by secretions from the lachrymal glands (tear glands) which lie above and to the outside of each eye. The fluid contains the enzyme lysozyme which kills bacteria. After passing over the conjunctiva, it drains from the eyes into the nasal cavity. The eyeball has a three layered structure. Structure of the eye Iris - regulates the amount of light entering through the pupil. Iris is a continuation of the choroid. Pigmented, colour of eye. WALL OF EYE IS COMPOSED OF THREE LAYERS: (a) Sclera Sclerotic - outer layer, tough protects and helps maintain shape of eye. White except at front where transparent - called cornea. (b) Choroid - middle layer, vascular, feeds retina cells. In humans, cells contain a black pigment melanin, which prevents light reflection in the eye. (c) Retina - inner layer, light sensitive cells - cones and rods. Fovea (yellow spot) in man only cones found here. Blind spot, retinal absent - where optic nerve leaves eye. Filled by jelly-like vitreous humour containing about 99% water,

  • Word count: 3286
  • Level: AS and A Level
  • Subject: Science
Access this essay

How does a microscope work?

Liban Ahmed Experiment 1 September 15, 2003 Activity 1: The Microscope Problem How does a microscope work? Hypothesis A microscope enables an individual to see details that are otherwise too small to be seen with the unaided eye by the use of lenses and light to magnify an object. Materials * Prepared slide * Microscope * Microscope slide * Cover slip * Medicine dropper * Lens paper * Newspaper samples from the colored comics and classified ads Procedure Part A-Using the Microscope . Brought a microscope to the lab area making sure to use both hands to carry the microscope and that the cord was not dangling. 2. Looked through the instructions making sure there were no problems that could be posed. 3. Organized the lab area and prepared all equipment including slides and the microscope. 4. Placed the prepared slide on the stage making sure the stage clips held the stage in place. 5. Switched to the low-power objective lens and focused on the image. 6. Recorded observations and calculated magnification. 7. Switched to the medium-power objective lens and focused on the image. 8. Recorded observations. 9. Moved the slide from one side to the other. 0. Recorded observations and calculated magnification. 1. Switched to the high-power objective lens and focused on the image. 2. Recorded

  • Word count: 873
  • Level: AS and A Level
  • Subject: Science
Access this essay

Investigation of the chromatic aberration of a converging lens.

Investigation of the chromatic aberration of a converging lens By Wen Yan Gao Aim To find the difference in focal length of a converging lens when used to produce images with red and blue light. Planning Background information Chromatic aberration arises from dispersion- the property that the refractive index of glass differs with wavelength of light. The focal length of a lens is determined by a combination of its geometry and the refractive index of the material from which it is made. The refractive index varies slightly with the wavelength of the light that is being transmitted. This means that the focal length of a lens will vary for different colours of light. For blue light (short wavelengths), the focal length is larger than that of red light (long wavelengths). Prediction It was predicted that the values of the focal length of the lens obtained from red and blue light are different, given that the standard focal length is 10cm. Proposed Method: The method is to use the lens formula. 1/f = 1/u +1/v To use this formula both the object distance (u) and the image distance (v) need to be measured. This method is not as simple as method 1 above, but the result obtained will be more accurate. Therefore, the focal length of a converging lens in this experiment was determined by method 2. Detailed Procedures: All the lights were switched off to ensure the

  • Word count: 960
  • Level: AS and A Level
  • Subject: Science
Access this essay

Ray tracing

Physics GCSE coursework Ray tracing The objective of this experiment is to find the length of an object and its focal lengths. I will first try to hypothesize where the length points will be. The given results of my hypothesized diagrams will determine the lengths of the focal points. I will then be able to find out where the object image will be situated by following my ray trace diagrams. I believe that I will be able to find the length of the object image if I can find the two focal length points ( 1/v and 1/u displayed in my ray trace diagrams and the focal graph). To achieve this I have decided that I could not get an accurate hypothesis if I did not know this information, so I will carry out a small practical experiment. 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. I then carried out an experiment to prove my hypothesis. I used light boxes to create a light source, but this is not extremely accurate as the light rays diverge and are not parallel. I used a screen and a lens to try to find an image. My results for my experiment were as follows. I had three

  • Ranking:
  • Word count: 635
  • Level: AS and A Level
  • Subject: Science
Access this essay

An essay on Electron Microscopy

An essay on Electron Microscopy An electron microscope (EM) shows the essential features of a cell. This uses an electron stream which is directed at the specimen. This invention was built in the 1930's. The transmission electron microscope (TEM) has extremely high magnification and resolution properties. The reason why biologists need a high resolution is in able to see the specimen in more detail. Feature Electron microscope Wavelength Electron beam - 1.0 nm Resolution 0.5 nm Maximum useful magnification X 250 000 Image Black and white - colour enhanced By computer Specimens Non-living Advantages Very high resolution- can see Plenty of cell detail Focused by Magnets Illumination Electrons The way an image is formed on a electron microscope (EM) is by the electrons in an electron microscope (EM) are focused. Here the particles or the membranes in cells can be seen as separate objects if they are further apart than half of the wavelength of the beam of the electrons used. Electron microscopes have a high resolution because the electron beams have a shorter wave length. Also the other reason why biologists need a high resolution is in able to see the specimen in more detail. The table below gives information about an electron microscopy: The development of electron microscope (EM) has had a huge impact on biology. Due to the fact that the

  • Word count: 448
  • Level: AS and A Level
  • Subject: Science
Access this essay

Electron and Gravitational Lenses

Electron and Gravitational Lenses The electron microscope uses special lenses to focus a beam of electrons rather than light. Two types of electron lenses are used in electron microscopes: electrostatic and electromagnetic. They create electric and electromagnetic fields to both concentrate and move the beam of electrons. The magnification in magnetic electron microscopes is determined by the strength of the current passing through the electric and electromagnetic lens coils. The image is focused by changing the current through the objective lens coil. Massive objects in the universe can act as lenses by bending the path of light that passes near them. If a light source is behind a massive galaxy, as seen from Earth, deflected light may reach the Earth by more than one path. Operating like a giant gravitational lens that focuses light along different paths, the gravity of the galaxy may make a single light source appear as two or more sources. Astrophysicists can use this phenomenon to determine the masses and densities of celestial bodies and thereby study their composition. Electron Microscopes In 1924 the French physicist Louis de Broglie suggested that electron beams might be regarded as a form of wave motion, similar to light. Furthermore, he reasoned that the actual wavelength of such a beam would be much shorter than that of a beam of light. The first

  • Word count: 667
  • Level: AS and A Level
  • Subject: Science
Access this essay