compound microscope

principles, application, parts,advantages & magnification

1. Compound microscope & IMAGE FORMED BY CONVEX LENSES.

2. Image Formation by Convex Lenses: When an object is placed at infinity , the real image is formed at the focus. The size of the image is much smaller as compared to that of the object.

3. When an object is placed behind the center of curvature , the real image is formed between the center of curvature and focus. The size of the image is same as compared to that of the object.

4. When an object is at the center of curvature , the real image is formed at the other center of curvature. The size of the image is same as compared to that of the object.

5. When an object is placed in between the centre of curvature and focus , the real image is the formed behind the center of curvature. The size of the image is smaller as compared to that of the object.

6. When an object is placed at the focus , a real image is formed at infinity. The size of the image is much larger as compared to that of the object.

7. When an object is placed in between focus and pole , a virtual image is formed. The size of the image is larger as compared to that of the object.

8. The term “compound” in compound microscopes refers to the microscope having more than one lens. Devised with a system of combination of lenses, a compound microscope consists of two optical parts, namely the objective lens and the ocular lens.

9. Working Principle of the Compound Microscope The specimen or object, to be examined is usually mounted on a transparent glass slide and positioned on the specimen stage between the condenser lens and objective lens. A beam of visible light from the base is focused by a condenser lens onto the specimen . The objective lens picks up the light transmitted by the specimen and creates a magnified image of the specimen called the primary image inside the body tube. This image is again magnified by the ocular lens or eyepiece.

10. Parts of Compound Microscope Mechanical parts Used to support and adjust the parts Magnifying parts Used to enlarge the specimen Illuminating parts Used to provide light

11. MECHANICAL PARTS Base or foot- basal structure that supports all the remaining parts of the microscope. Pillar- small, strong vertical projection developing from the foot. Arm- curved and strong structure used for handling the entire instrument. Inclination joint- joint at which the arm is attached to the pillar of the microscope. Used for tilting the microscope. Stage- flat rectangular plate where slide is placed. A hole is present in the center of the stage. Light rays pass through the hole.

12. MAGNIFYING PARTS Ocular/ eye piece- lens found at top of the body tube which functions to further magnify the image produced by objective lens. Objectives- are the primary optical lenses on a microscope. They range from 4x- 100x.

13. ILLUMINATING PARTS Mirror- located beneath the stage and has concave plane surface to gather and direct light on order to illuminate the object. Iris diaphragm- regulates the amount of light necessary to obtain a clearer view of the object Condenser- set of lenses between the mirror and stage that concentrates light rays on the specimen.

14. MAGNIFICATION Magnification is the ability to view an object larger. The magnification of a compound microscope is given by: M= where, D= least distance of distinct vision(25 cm) L= length of the microscope tube Fo = focal length of the objective lens Fe= focal length of the eye piece The highest total magnification is 1000x for a compound microscope.  

15. Applications A compound microscope is of great use in pathology labs so as to identify diseases. Various crime cases are detected and solved by drawing out human cells and examining them under the microscope in forensic laboratories. The presence or absence of minerals and the presence of metals can be identified using compound microscopes. Students in schools and colleges are benefited by the use of a microscope for conducting their academic experiments. It helps to see and understand the microbial world of bacteria and viruses, which is otherwise invisible to the naked eye. Plant cells are examined and the microorganisms thriving on it can be ascertained with the help of a compound microscope. Thereby, a compound microscope has proved to be crucial to biologists.

16. Advantages Simplicity and its convenience. A compound light microscope is relatively small, therefore it’s easy to use and simple to store, and it comes with its own light source. Because of their multiple lenses, compound light microscopes are able to reveal a great amount of detail in samples.

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