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  • ICAR and TNAU E-Course Summarized

    Summarized Notes
  • Which of the following have the highest magnification?

    Question: Which of the following have the highest magnification?

    Options:

    Simple microscope
    Compound microscope
    Phase contrast
    Oil immersion microscope

    ✅Explanation:
    Oil immersion microscopes achieve the highest magnification among the options listed. They use a special oil with a refractive index similar to glass, placed between the objective lens and the specimen. This oil minimizes light refraction, allowing more light to enter the objective lens and resulting in a clearer image with higher resolution and magnification, typically up to 1000x.

    🔑Key Points:
    -Microscopes are important laboratory instruments that are used to enlarge the image of an object many-folds.
    -This helps us to study biological specimens like cells and cell structures that are too small for the naked eye and are termed as 'microscopic'.
    -However, not all types of microscopes can be used for observing all specimens.
    -Each microscope requires the specimen to be prepared in a specific way.
    -This determines which microscope suits which type of specimen.
    -Most of the microscopes require the specimens to be stained, which eventually kills them.
    -So in order to view living cells, we need to use unstained specimens.
    -The microscope used for study of living cells is phase-contrast microscope.
    -Phase-contrast microscopy is based on the principle that small changes in the phase can be transformed into changes in brightness of that object.
    -This can be observed as difference in image contrast.
    -Phase objects refer to unstained specimens that do not absorb light.
    -This microscopy technique is suitable for living cells because unstained specimens are used, keeping the cells alive.
    🛑Additional Information
    -Compound microscope –
    -It is a type of optical microscope that uses two lenses instead of one to have a better resolution image.
    -The lenses are known as ocular lens and objective lens.
    -It generally uses visible light to view the specimens.
    -Oil-immersion microscope –
    -It is used to increase the resolution of a light microscope.
    -It uses a transparent oil to immerse the objective lens as well as the specimen.
    -The oil has a high refractive index, allowing increased aperture of the lens.
    -Light tends to bend (refract) whenever it changes a medium.
    -Oil and glass have similar refractive indices and so they function as almost the same medium causing minimum or no refraction.
    -This creates a sharper image of the specimen.
    -Electron microscope –
    -It is a type of microscope that uses an electron beam instead of a beam of light as the source of illumination.
    -It can be used to observe both biological as well as non-biological specimens.
    -They have higher magnification and higher resolution than light microscopes.
    -Compound and oil-immersion microscopes cannot be used for living cells as they use stained specimens.
    -Electron microscopes require the specimens to be kept in vacuum, which kills living cells.

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