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KS3 Biology

Topic 1: Cells and organisation

Microscopy

Microscopy

Animal and plant cells

Specialised cells

The movement of substances

Unicellular organisms

Levels of organisation

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Objectives

  • Explain the necessity of using a microscope to observe cells.

  • Identify the main parts of a light microscope.

  • Describe the basic steps for using a microscope to view a specimen.

Why use a microscope?

  • All living organisms are made up of cells, which are the basic building blocks of life.

  • Cells are too small to see with the naked eye so to observe cells you need to use a microscope, which magnifies the image.

  • The parts of a microscope include the eyepiece, objective lens, stage, coarse focus wheel, fine focus wheel, and light source.

  • To view an object down the microscope, the object you observe should be thin enough for light to pass through. You may need to add a stain or dye to make the object easier to see. Samples are usually prepared on a microscope slide.

Steps to use a microscope

  1. Place the microscope slide with the object you want to observe on the stage.

  2. Select the objective lens with the lowest magnification.

  3. Look through the eyepiece and adjust the focus using the coarse focus wheel.

  4. Use the fine focus wheel to bring the object into sharp focus.

  5. Repeat steps 3 and 4 with a higher magnification objective lens to see the object in more detail.

  6. Draw what you can see, and add labels for any parts you know.

 A light microscope.

Key words

  • Microscope: An instrument used to make objects that are too small to see with the naked eye appear larger.

  • Magnifies: Makes something look bigger than its actual size.

  • Cells: The basic units that make up all living organisms, typically too small to be seen without magnification.

  • Eyepiece: The lens part of the microscope that the user looks through.

  • Objective lens: The lens on the rotating nosepiece closest to the specimen, which provides different levels of magnification.

  • Coarse focus wheel: A control used for initial, large adjustments to focus the image.

  • Fine focus wheel: A control used for small adjustments to bring the image into sharp focus.

Extension ideas

  1. Calculate the total magnification achieved when using different objective lenses.

  2. Research different types of microscopes (e.g., electron microscopes) and when they would be used instead of a light microscope.

Related topics

Animal and plant cells

Specialised cells

Unicellular organisms

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