This exam tips covers Exam Tips: Microscopy within Microscopy for GCSE Biology. Light and electron microscopes, magnification and resolution calculations, specimen preparation, staining techniques, and practical microscopy skills It is section 19 of 19 in this topic. Treat this as a marking guide for what examiners are looking for, not just a fact list.
Topic position
Section 19 of 19
Practice
18 questions
Recall
20 flashcards
Exam Tips: Microscopy
Common Question Types:
- Magnification calculation (2-3 marks): Use the formula M = I/A. Show all working, check units match, remember magnification itself has no units
- Compare microscope types (3-4 marks): Always compare both types directly in each point — "light microscope can view living specimens, whereas electron microscope cannot"
- Explain why electron microscope is used (2 marks): Must mention resolution, not just magnification — "resolution is too low in a light microscope to see [structure]"
- Describe microscopy method (3 marks): RPA1 — start at lowest power, coarse then fine focus, add stain, lower coverslip at 45 degrees to avoid air bubbles
- Explain why staining is used (1-2 marks): Cells are transparent/colourless; stains bind to specific structures to make them visible
Key Command Words:
- "State" — one-word or short phrase answer, no explanation needed
- "Calculate" — show full working, give units, check magnitude makes sense
- "Describe" — say what it does or what you observe, no reason needed
- "Explain" — must give a reason using "because" — this is where marks are won or lost
- "Compare" — you MUST reference both things being compared in every sentence
- "Suggest" — use your knowledge to give a sensible reason, even if not directly taught
Common Mistakes to Avoid:
- Confusing magnification (size) with resolution (clarity) — they are completely different properties
- Using the coarse focus knob at high magnification — this can crack the slide or scratch the lens
- Forgetting to convert units before calculating — mixing mm and μm gives a wrong answer
- Saying electron microscopes can view living cells — they absolutely cannot (vacuum kills all specimens)
- Writing units for magnification — magnification is a pure ratio (no mm, no x-units in the final answer)
- Saying stains make cells bigger — stains only add colour, never magnify