This definitions covers Key Definitions: 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 13 of 19 in this topic. Make sure you can use the exact wording confidently, because definition marks are often lost through vague language.
Topic position
Section 13 of 19
Practice
18 questions
Recall
20 flashcards
Key Definitions: Microscopy
- Magnification
- The number of times larger an image appears compared to the actual size of the object. Calculated as: Magnification = Image size / Actual size.
- Resolution
- The ability to distinguish two points that are very close together as separate, distinct objects. High resolution produces a sharp, clear image. Resolution in a light microscope is limited to about 200 nm by the wavelength of visible light.
- Light microscope
- A microscope that uses visible light and glass lenses to magnify specimens. Maximum magnification approximately x1500, maximum resolution approximately 200 nm. Can view living specimens.
- Electron microscope
- A microscope that uses a beam of electrons rather than light to produce highly magnified images. Maximum resolution is far superior to a light microscope (down to 0.05 nm) but specimens must be dead and prepared in a vacuum.
- Transmission Electron Microscope (TEM)
- An electron microscope where the electron beam passes through a very thin specimen, producing a 2D image of internal structures. Resolution: 0.05 nm. Used to study internal organelle detail.
- Scanning Electron Microscope (SEM)
- An electron microscope where the electron beam scans the surface of the specimen, producing a 3D-appearance image of external surface structures. Resolution: 3-10 nm.
- Objective lens
- The lens in a light microscope that is closest to the specimen. Provides the primary magnification. Common magnifications: x4, x10, x40, x100. Always start with the lowest power objective lens first.
- Eyepiece lens (ocular lens)
- The lens at the top of the microscope through which you look. Usually x10 magnification. The total magnification is eyepiece magnification multiplied by objective lens magnification.
- Staining
- Adding a chemical dye to a microscope specimen to make specific structures more visible. Most cells are transparent without staining. Common stains: iodine (stains starch purple/black), methylene blue (stains nuclei dark blue).
Must Memorise: Magnification = Image size / Actual size. The triangle: I over A x M. Cover the letter you want to find.
Must Memorise: Resolution = ability to distinguish two separate points. High magnification does NOT automatically mean high resolution.
Must Memorise: Electron microscopes use electrons (not light). They cannot view living specimens and require a vacuum.