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Reviewer participation may vary by guide. Checked against Cambridge IGCSE Biology 0610 (2026–2028); last reviewed August 2026.
What this skill means
Set up the microscope with the lowest power objective first, focus using the coarse then fine adjustment, and always start viewing at low power before switching to higher magnification. Biological drawings must be accurate, with clear lines, correct proportions, and magnification stated.
Microscope skills are tested every year in Paper 5 and Paper 6. You need to be able to use a microscope, make biological drawings from what you see, calculate magnification, and convert between units (mm and μm). These are reliable marks if you practise the correct technique.
Setting Up and Focusing
Place the slide on the stage and clip it in position
Select the lowest power objective lens (e.g. ×4 or ×10)
Looking from the side, lower the objective lens close to the slide using the coarse focus knob
Look through the eyepiece and slowly raise the objective using the coarse focus until the specimen comes into view
Use the fine focus knob to sharpen the image
To see more detail, switch to a higher power objective (e.g. ×40) and refocus using the fine adjustment only
Always start with low power because it gives a wider field of view, making it easier to locate the specimen.
Calculating Total Magnification
Total magnification = eyepiece lens magnification × objective lens magnification
For example: eyepiece ×10 and objective ×40 gives total magnification = ×400.
For drawing magnification: magnification = image size ÷ actual size
Always ensure both measurements are in the same units before dividing. If the image size is in mm and the actual size is in μm, convert one to match the other (1 mm = 1000 μm).
Rules for Biological Drawings
Use a sharp pencil and draw single clear lines (no shading, no colouring, no sketchy lines)
Draw the specimen large enough to fill at least half the space available
Keep proportions accurate: the drawing must reflect what you see
Label lines must be straight, horizontal, and drawn with a ruler, touching the structure they identify
Labels should be written outside the drawing, not inside it
Include a title (e.g. "Drawing of a transverse section of a leaf ×100") and state the magnification
Do not draw individual cells unless specifically asked: draw the tissue plan (outline of tissue regions)
Use this before submitting your answer
A complete answer is specific enough for another person to repeat or assess.
✓Always start with the lowest power objective lens.
✓Focus by raising the lens away from the slide, not lowering it towards it (to avoid crushing the slide).
✓State total magnification = eyepiece × objective.
✓Drawings: single clear pencil lines, no shading or colouring.
✓Drawings: proportions must reflect what is seen.
✓Labels: straight ruler-drawn lines, horizontal, with labels outside the drawing.
✓Include a title and magnification for every drawing.
✓Know unit conversions: 1 mm = 1000 μm.
Try the skill in a question (3 marks)
A student views a cell using an eyepiece lens of ×10 and an objective lens of ×40. The drawing of the cell is 60 mm long. Calculate the actual length of the cell in μm. Show your working. [3]
Show the answer and marking guidance
Total magnification = 10 × 40 = ×400
Actual size = image size ÷ magnification = 60 mm ÷ 400 = 0.15 mm
Convert to μm: 0.15 × 1000 = 150 μm
Original practice content written for this site. It is not an official Cambridge question.