This topic summary covers Knowledge Organiser: 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 18 of 19 in this topic. Use this topic summary to connect the idea to the wider topic before moving on to questions and flashcards.
Topic position
Section 18 of 19
Practice
18 questions
Recall
20 flashcards
Knowledge Organiser: Microscopy
Key Terms
- Magnification — how many times larger the image is than the real object (M = I/A)
- Resolution — ability to distinguish two separate points; determines image sharpness
- Light microscope — uses light and glass lenses; max x1500, max resolution 200 nm
- TEM — electrons pass through; 2D internal images; resolution 0.05 nm
- SEM — electrons scan surface; 3D-appearance images; resolution 3-10 nm
- Staining — adding dye to make transparent structures visible
- Eyepiece lens — lens you look through; usually x10
- Objective lens — lens closest to specimen; x4, x10, x40, x100
Must-Know Facts
- Magnification = Image size / Actual size (M = I/A)
- Total magnification = eyepiece x objective lens
- Light microscope resolution limit: ~200 nm (limited by wavelength of light)
- Electron microscope resolution: 0.05 nm (uses electrons, shorter wavelength)
- Light microscopes CAN view living specimens; electron microscopes CANNOT
- TEM = Through = 2D internal; SEM = Surface = 3D external
- Stains do NOT magnify — they add colour to transparent structures
- Unit ladder: mm x1000 = μm x1000 = nm
- Always start with lowest objective lens power first
- Always use fine focus knob (not coarse) at high magnification
Common Marks Lost
- Writing "magnification" instead of "resolution" when explaining image clarity
- Mixing units in calculations — always check both values are in the same unit
- Forgetting that magnification has no units (it is a ratio)
- Saying stains magnify cells — they only add colour
- Saying electron microscopes are just more powerful light microscopes — they use electrons, not light
- Not converting standard form to mm or μm before calculating
- Forgetting electron microscopes cannot view living specimens
- Confusing TEM (internal/2D) with SEM (surface/3D)