BTEC Applied Science Unit 1: Biology Microscopes

Types of Microscopes

Light Microscopes

• Components:
  • Specimen: Placed on a glass slide with a cover slip; should be thin enough for light to pass through.
  • Light Source: Usually shines light from below.
  • Stain: Can be used to highlight different parts of the specimen.
• Parts of the Microscope:
  • Eyepiece: Where you look through.
  • Objectives: Multiple objectives for changing magnification.
  • Stage: Where the slide is placed, can be adjusted up and down.
  • Focusing Knob: Moves the stage to focus the image.
• Images: Photographs taken through a light microscope.

Electron Microscopes

• Function: Fires a beam of electrons at the specimen.
  • Electrons pass through and are detected to form an image.
• Advantages:
  • Much higher magnification and better resolution than light microscopes.
  • Can see inside cells, revealing organelles.
• Disadvantages:
  • Very expensive and require special training.
  • Can only examine dead material due to exposure to high-energy electrons.
• Images: Referred to as electron micrographs.

Magnification Concept

• Equation: ( M = \frac{I}{A} )
  • ( I ) = size of the image.
  • ( A ) = actual size.
  • ( M ) = magnification.
• Example Calculation:
  • If actual size = 0.1 mm and image size = 20 mm, magnification is 200.
• Eyepiece Graticule: Scale for measuring image size, needs calibration.

Measurement and Conversion

• Units of Measurement:
  • Millimeter (mm): ( 1 \text{ mm} = 1 \times 10^{-3} \text{ m} ) (0.001 meters).
  • Micrometer (µm): ( 1 \text{ µm} = 1 \times 10^{-6} \text{ m} ) (0.000001 meters).

Important Considerations

• Understanding how to calculate magnification and being familiar with units of measurement is critical.
• Electron microscopes provide more detailed images but have limitations in terms of cost, training, and specimen viability.