This exam focus covers Exam Focus: 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 16 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 16 of 19
Practice
18 questions
Recall
20 flashcards
Exam Focus: Microscopy
Exam FavouriteTypical Question Types
- Magnification calculations (2-3 marks) — These appear in almost every AQA Biology Paper 1. Expect to calculate actual size, image size, or magnification using the formula. Always show working and give units.
- "Explain why an electron microscope is used rather than a light microscope" (2 marks) — The answer must mention resolution, not just magnification. Say: "The electron microscope has a higher resolution than a light microscope, allowing structures smaller than 200 nm (such as ribosomes) to be seen clearly."
- Compare light microscope and electron microscope (4 marks) — Examiners want a direct comparison for each point. Use "whereas" or "however": "A light microscope can view living specimens, whereas an electron microscope cannot as specimens must be prepared in a vacuum."
- Describe the method for using a light microscope (3-4 marks) — Based on RPA1. Expect to describe: start at lowest magnification, use coarse focus then fine focus, add stain, lower coverslip at 45 degrees.
- Explain why staining is used (1-2 marks) — "Most cells are transparent and colourless. Stains bind to specific structures, making them visible under the microscope."
Mark Trap: "Magnification" vs "Resolution"
The most common mark lost in this topic is using "magnification" when the answer requires "resolution." Examiners specifically check for this distinction. If a question says "explain why the image is not clear enough to see detail," the answer is about resolution — not magnification. Practise explaining the difference until it becomes automatic.
Standard Form in Calculations
Cell measurements in exams are often given in standard form (e.g., 2.5 x 10^-5 m). Make sure you can convert these to mm or μm before substituting into the magnification formula. A very common error is mixing units — always check both measurements are in the same unit before dividing.