2.2.2 Microscopy & Drawing Scientific Diagrams

Microscopy:

1. Types of Microscopes:

• Light Microscope:
• Uses light to form an image.
• Can view live specimens.
• Maximum magnification: x1500.
• Resolution: 200 nm, limited by the wavelength of light.
• Electron Microscope:
• Uses beams of electrons for imaging.
• Higher magnification and resolution than light microscopes.
• Types:

1. Transmission Electron Microscope (TEM):

• Produces detailed 2D images of internal structures.
• Maximum resolution: 0.1 nm.

2. Scanning Electron Microscope (SEM):

• Produces detailed 3D images of surfaces.
• Resolution: 10 nm.

2. Key Terms:

• Magnification: How much larger the image is compared to the actual size of the object.
• Formula:

$$\text {Magnification = Size of Image ÷ Actual Size}.$$

• Resolution: The ability to distinguish between two close points as separate objects.

3. Preparation of Specimens:

• Staining: Used to enhance contrast by colouring specific structures (e.g., methylene blue for nuclei).
• Sectioning: Thin slicing of samples for clearer viewing under a microscope.

Drawing Scientific Diagrams:

Image: This is a student drawing at high power detailing cells in a transverse section of the lamina of a shade leaf of beech (a different part of the same leaf shown in Figure 5a). The student has correctly included a title and scale bar. The student has labelled the drawing and there is good use of annotation. The drawing itself is detailed and clear. (Note: the cell walls of all the plant cells have been drawn; this is because they were visible with the microscope and slide used. It is not always possible to see this much detail using a classroom light microscope).

4. Guidelines for Scientific Diagrams:

• Use a sharp pencil for clear lines.
• Avoid shading or colouring.
• Ensure diagrams are large and clear.
• Label structures with straight lines, not crossing each other.

5. Labelling and Annotations:

• Include the name of the specimen and magnification used.
• Labels should:
• Be horizontal.
• Include specific terms (e.g., nucleus, mitochondrion).

6. Proportions:

• Accurately represent the relative size of structures.
• Use grid paper if necessary to maintain proportions.

7. Scale Bars:

• Include a scale bar to indicate actual size.