Microscopy — required practical

AQA GCSE Biology

Use a light microscope to observe cells and calculate magnification.

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Method

  1. Prepare a slide: add a drop of water/stain, place the specimen, lower a cover slip at an angle to avoid air bubbles.
  2. Start on the lowest-power objective, focus with the coarse then fine focus.
  3. Switch to higher power to see more detail; draw and label what you see.

Results & analysis

Magnification = size of image ÷ size of real object. Total magnification = objective lens × eyepiece lens. Rearrange the equation to find real size if given image size and magnification.

Risk assessment

  • Care with glass slides and cover slips (sharp); use stains carefully.

Improving accuracy & reliability

  • Focus on low power first to avoid cracking the slide.
  • Add a stain (e.g. iodine) to make structures visible.
Exam tip: Learn magnification = image ÷ actual, and be ready to rearrange it and convert units (mm ↔ µm; 1 mm = 1000 µm).

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