Required Practical 1

RP1: Microscopy — Half-Page Notes

Aim:
Use a light microscope to observe cells and calculate magnification and cell size.

Slide preparation:

• Place a thin sample on a slide

• Add one drop of stain (e.g. iodine)

• Lower coverslip at an angle to avoid air bubbles

• Blot excess stain

Using the microscope:

• Start on lowest magnification

• Use coarse focus, then fine focus

• Increase magnification if needed

• Adjust light for clarity

Why stains are used:

• Cells are transparent

• Stains make structures (e.g. nucleus, cell wall) visible

Magnification formula:

Magnification = Image size / Actual size so therefore also:

• Actual size = image size ÷ magnification

• Image size = actual size × magnification

Units:

• 1 mm = 1000 μm

Measuring cell size:

• Measure image with a ruler

• Convert units

• Divide by magnification

Safety:

• Carry microscope with two hands

• Handle slides carefully

• Do not touch stains