Lens and Image
Lens and Image
1. What happened to the stage when you turned the knob anti-clockwise (away from you)? The stage will move up when turned the coarse adjustment knob (large knob) anti- clockwise.
2. What happened to the stage when you turned the knob clockwise (toward you)? The stage will move down when turned the coarse adjustment knob (large knob) clockwise.
3. Observe the letter ‘I’ under low (i.e. objective X4 ) magnification. What do you notice about the image? The image of letter ‘I’ under low magnification is inverted/upside down.
4. Move the slide slowly to the left. What happens to the image? The image will move to the right when the slide move slowly to the left.
5. Centre a letter. Now move the slide slowly away from you. What happens to the image? The image appears nearer (towards us) when the slide move slowly away from us.
6. How far does the stage move from one complete turn of the fine adjustment knob? – estimate; view from side. The stage move up with such a small distances that is hard to be noticed after one complete turn of the fine adjustment knob.
7. Completely close the iris diaphragm. What effect has this had on your ability to see? Completely close the iris diaphragm affect the ability to see by decreasing the brightness and increasing the contrast. The image produced is dim and not clear at all.
8. Now gradually open the diaphragm record the effect on: Intensity of light; The intensity of light increase Your ability to see; The image become bright and clearer
9. Focus on the image, set the diaphragm so illumination is minimal. Move the condenser gradually so that it is as close to the slide as it can go. Move the condenser as far away from the slide as you can. What happens? The light intensity will decrease.
10. Now carefully rotate x10 objective into the light path. If necessary, bring image into focus by turning the fine focus knob only. What has happened to the degree of details you can see in the letter ‘I’ and surrounding paper? The letter ‘I’ can only be seen for a small portion under the x10 objective lens.
11. Open the diaphragm; can you still see the actual strands within the paper? Yes, the actual strands are within the paper when open the diaphragm.
12. Move the slide slowly to the right. What happens to the image? The image move to the left when the slide move to the right.
13. Did you notice any difference from the same procedure using the 4x objective? Try your hand again with the 4x objective. Yes, the 4x objective lens provide clearer and overall image.
14. Carefully and slowly rotate 40x objectives into place. Ensure the objective doesn’t CRASH into slide. If you encounter any resistance, STOP! Is the image in focus? No, the image is not in focus.
15. If not, use the FINE adjustment only. Note the close proximity of the 40x objective and the slide. Any large movements produced by the coarse adjustment will cause the objective to crash through the slide. Is your illumination adequate?
The illumination is not adequate.
16. Open the diaphragm and record the changes. The image is clearer and brighter.
17. Move the condenser up and down. Does your eye detect any changes produced by movement of the condenser? Yes, the condenser moving upwards will provide a clearer and bright image while the condenser moving downwards providing a dim image.
Discussion: Technology is used extensively by scientists in their laboratory work. One essential piece of technology is the microscope. In this experiment, certain skills of microscopy will be enhanced by learning the parts of the microscope, how to measure under the microscope, and gaining familiarity with the rules when using microscope. Scientists use the scientific method to study or investigate nature or the universe (Steven D. , 1997). The process of science will be understood better by looking at components of this method and by doing some steps. A microscope is an instrument for producing enlarge images of objects too small to be seen unaided (O. A. F. Ilusanya, 2009).
The word of “micro” refers to tiny and “scope” refers to view or look at. Microscopes range from a simple magnifying glass to the expensive electron microscope. The compound light microscope is the most common instrument used in laboratory. It is an instrument contains two lenses which magnifies and a variety of knobs to focus the object. The features of the microscope and the function of the component part should be learned before discuss the experiment. Eyepieces of microscope are also known as oculars which are the lenses to view the magnified image. The magnification capability of the oculars is x10.
Microscope should be handled carefully by carrying it with both hands, one on the base and the other on the arm of microscope at all times. Bottom of FormRevolving nosepiece is the assembly which contains the various objective lenses and can be viewed at different magnifications. Stage is the platform which the object is placed to be examined. The function of the condenser is to provide a cone of light to illuminate a specimen (Suzanne B. & Keith M. 2010, p. 30). The iris diaphragm at the top of the condenser controls the amount of light that is delivered through the aperture of the stage.
The diaphragm is adjusted by a lever or a wheel on our microscopes. The light coming through the microscope can be adjusted by turning the light switch or by adjusting the iris diaphragm. Higher magnifications usually require more light. Illuminator is the light source. Coarse and fine adjustment knobs are used to adjust the distance between the objective lens and the stage. This distance is called the working distance. All the lenses have to be clean to avoid a blurry image. The lenses can be cleaned by using the lens paper. Handkerchief should not be used because it may damage the lens.
One should not breathe when cleaning the lens, since this can leave a film when wiped off. To clean a lens, it should be wiped gently with a circular motion. The method of focusing an object by using microscope is discussed. Firstly, the slide should be placed at the centre of the stage and start to focus with low power. The slide and objective are brought very closely together by using the coarse adjustment. When looking through the microscope, the object is focused by turning the coarse adjustment knob, thus the distance between the slide and objective increases until the image can be seen.
Then the image is sharpen with the fine adjustment knob. After revolving the nosepiece to high power, only the fine focus knob is used to adjust, as it may break the slides if the coarse adjustment knob is used. When changing from low to high power, more light is also required to view the image. In this experiment, a letter “i” is observed by using a microscope to discover how a microscope works the effect of letter “i” see through the eyepiece and the changes occur when changing the focus and power. The image seen through the eyepiece and the actual image on the stage are different.
The image is inverted 180 degrees. When the slide is move to the left of the stage. Image observed under the light microscope are reversed because it is a compound microscope with two lenses. By having two lenses, they reflect the images on the stage. Besides that, when the slide moves to the upper right area of the stage, the image through the eyepiece moves to the lower left area. Similarly, when the slide moves to the left of the stage, the image moves to the right. The intensity of light changes when the diaphragm moves. The image gets darker as the diaphragm moves left and vice versa.
As the magnification increases the working distance of the microscope seems to get smaller. Because of the specimen is not centred in the field of view on low power before going to the high power, then it is hard to refocus on the high power. This basically means that as the objective becomes higher, the field of view narrows, which makes it hard to see the specimen on high power. As stated above, the condenser controls the quality of light which reaches the slide while the diaphragm controls the quantity of light reaching the slide.
If it is too low refraction, it will cause distortion during focusing the object. To control the amount of light reaching the slide adjust only the diaphragm. When the diaphragm is on the largest opening, the greatest resolution of light is obtained. A microscope may have one or more objectives each with of different magnifications. The second lens is the eyepiece or ocular lens which is located at the top of the microscope. The common eyepiece lens magnifies ten times (x10). To calculate magnification of the object being viewed is to multiply the power of the objective lens by the power of the ocular.
University/College: University of Chicago
Type of paper: Thesis/Dissertation Chapter
Date: 18 October 2016
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