Microscopy

• Cells and their structures are too small to be seen with the naked eye, so a microscope is needed to view them. 

• Here’s how to prepare a slide to observe under a light microscope:

  • Cut a thin section of the specimen to allow light to pass through.

  • Using forceps, place the thin specimen on a microscope slide.

  • Add a drop of stain (e.g., iodine solution for plant tissue) to make cell parts, which are usually colourless, more visible.

  • Carefully place a cover slip over the specimen, lowering it gently to avoid trapping air bubbles.

  • Place the slide on the microscope stage. Start with the lowest magnification lens. While looking from the side, use the coarse focus wheel to bring the slide close to the lens, but without touching. 

  • Then, look down the eyepiece and adjust the focus:

    • Use the coarse focus wheel first to lower the slide and bring the image into view.

    • Refine the focus with the fine focus wheel.

    • For higher magnification, switch to a higher magnification lens and fine-tune the focus with the fine focus knob.

• In microscopy, magnification can be calculated using the formula:

magnification = size of image / size of real object

• In this formula:

  • Size of image is how large the object appears under the microscope.

  • Size of real object is the actual size of the object being viewed.

• When biologists observe and draw what they see under a microscope, the drawing represents the image, and the real object is the actual cell or structure. 

• The magnification shows how much the object has been enlarged in the drawing.

• To work with very large or very small numbers in a manageable way, scientists use standard form. 

• This notation expresses numbers with a single digit before the decimal, followed by "x10" raised to an exponent, which represents the number of places the decimal has moved.

• Examples:

  • 0.001 can be written as 1 x10-3

  • 170,000 can be written as 1.7 x105

  • 0.0000823 can be written as 8.23 x10-5

• Using standard form helps simplify calculations and comparisons, particularly when dealing with extremely small or large measurements in microscopy.

• Microscope: An instrument used to magnify objects too small to be seen with the naked eye.

• Magnification: The process of making an object appear larger than its actual size.

• Resolution: The ability of a microscope to distinguish between two separate points, resulting in a clear image.

• Light microscope: A microscope that uses visible light and lenses to produce a magnified image.

• Electron microscope: A microscope that uses a beam of electrons and electromagnets to produce a highly magnified and resolved image.

• Standard form: A way of writing very large or very small numbers using powers of 10 (e.g., 1×10−3).

• Size of image: The apparent size of an object as seen through a microscope or in a drawing.

• Size of real object: The actual, true size of the object being viewed.

• Specimen: A sample of biological material prepared for observation under a microscope.

• Microscope slide: A flat piece of glass used to hold a specimen for microscopy.

• Stain: A chemical substance added to a specimen to make structures more visible under a microscope.

• Cover slip: A small, thin piece of glass placed over a specimen on a slide to protect the lens and hold the specimen flat.

• Microscope stage: The platform on a microscope where the slide is placed.

• Coarse focus wheel: A control knob used for large adjustments to the distance between the lens and the slide, bringing the image into initial focus.

• Fine focus wheel: A control knob used for small adjustments to the distance between the lens and the slide, refining the focus for a sharp image.

• Biological drawing: A scientific drawing of a specimen observed under a microscope, showing key structures accurately and to scale.

• Scale: The proportional relationship between the size of a drawing and the actual size of the object it represents.