Lecture Notes: Calculating Microscope Image Measurements

Learning Goals

• Calculate Total Magnification
• Calculate Field of View (FOV) of High Power Lens
• Measure Specimen Size

Total Magnification

• Definition: Total magnification is the product of the magnification of the ocular lens and the objective lens.
• Examples:
  • Ocular lens: 10x, Objective lens: 4x → Total magnification: 40x
  • Ocular lens: 10x, Objective lens: 10x → Total magnification: 100x

Field of View (FOV)

• Definition: The diameter of the circle of light visible through a microscope.
• Low/Medium Power:
  • Use a ruler to measure (place ruler under the microscope and count mm across the field of view).
  • Example: Field of view = 4 mm
• High Power:
  • Ruler is not effective (field of view < 1 mm).
  • Calculation needed:
    • Equation: HP Diameter = (Low Power Magnification x Low Power Diameter) / High Power Magnification
    • Example: Given Low power magnification: 40x, Low power diameter: 2 mm, High power magnification: 400x
      • HP Diameter = (40 x 2) / 400 = 0.2 mm

Specimen Size

• Equation: Specimen Size = FOV / Number of Specimens Across Diameter
• Examples:
  • Green Specimen:
    • FOV: 4 mm, 2 specimens across
    • Size = 4 / 2 = 2 mm
  • Yellow Specimen:
    • FOV: 4 mm, 10 specimens across
    • Size = 4 / 10 = 0.4 mm
  • Red Specimen:
    • FOV: 4 mm, 3 specimens across
    • Size = 4 / 3 ≈ 1.3 mm
  • Brown Specimen:
    • Same calculation as Red
    • Size ≈ 1.3 mm

Conclusion

• Ensure you can:
  • Calculate total magnification
  • Calculate high power field of view
  • Measure specimen size
• Review the lecture video or ask questions in class if needed.

Please revise these concepts if necessary and feel free to reach out with any questions!