Microscope Magnification and Measurement

Microscopy and Cells

• Millimeters (mm) measure distances across the field of view on scanning power, whereas micrometers (μm) are used for greater magnification.
• Fields of view and approximate distances across for scanning, low, and high power are:
  • Scanning power: 4 mm
  • Low power: 1.2 mm
  • High power: 0.3 mm

Magnification and Resolution

• Typical magnifications available with a set of objectives are 10x (low power), 40x (high power), and 100x (oil immersion).
• Eyepieces usually have a magnification between 8x and 12.5x.
• The resolution and numerical aperture of the microscope allow for the exposure of subunits within the sample.
• The microscope's resolving power is determined by the limit of resolution (l.r.), which specifies the smallest distance at which two neighboring points can still be observed as separate entities.
• The limit of resolution for a microscope is calculated using the Abbe equation: l.r. = 0.61 λ / N.A.

Limit of Resolution

• The l.r. of the naked eye is approximately 0.1 mm.
• A high-quality microscope has an l.r. of about 0.2 μm, providing a 500-fold improvement.
• The limit of resolution is indirectly proportional to N.A.
• As N.A. increases, the resolving power of the microscope also increases.

Cell Biology

• Cells are considered to be the fundamental building block of all biological life.
• Cells possess all the necessary characteristics of life, making them critical to our understanding of the processes that govern living organisms.
• The study of cells is indispensable to the study of life itself.

Microscopy

• Microscopy is the technical field of using microscopes to view samples or specimens.
• Two types of microscopes are named according to the source of illumination used: light microscopes and electron microscopes.
• Light microscopy employs visible light to detect small objects.
• Examples of light microscopy include bright, dark, phase-contrast, and fluorescence microscopy.
• Fluorescence microscopy is a technique used to observe live samples in real time.
• It involves using fluorescent molecules to tag and light up target cells or cellular components, mostly proteins.