Microscopy.
Types of Microscopes.
- Microscopy is a technique used to visualize small objects or structures that are not visible to the naked eye.
- The sources describe two main types of microscopes: light microscopes and electron microscopes.
Light Microscopy
- Light microscopes use light to illuminate the specimen.
- They have a resolving power of 0.2um. This means objects smaller than this cannot be distinguished, and if two objects are closer than this they cannot be seen as separate.
- The basic light microscope uses light that passes through the object, which is then magnified by the objective and eyepiece lenses.
- There are several types of light microscopes:
- Bright-field microscopy: Uses ordinary light to view stained preparations. The microscope includes a condenser, objective lens, and eyepiece.
- Fluorescence microscopy: Uses fluorescent dyes that bind to specific cellular components. Some dyes (e.g., DAPI, Hoechst) bind to DNA. Antibodies labeled with fluorescent compounds are also used.
- Phase-contrast microscopy: Does not require staining, as it measures the time taken for light to pass through the object. This allows for viewing living cells. A variation is differential interference microscopy, which creates a 3D image.
- Confocal microscopy: Uses a sharp, focused light (e.g., a laser). Images are stitched together on a computer, reducing light exposure and producing a clearer image. It uses a pinhole aperture to improve resolution.
- Polarizing microscopy: Uses polarized light (light vibrating in one direction) to make highly organized macromolecules visible.
Mnemonic for Light Microscopes
To help remember the types, use the mnemonic "Big Friendly Pandas Can Play":
- B for Bright-field microscopy
- F for Fluorescence microscopy
- P for Phase-contrast microscopy
- C for Confocal microscopy
- P for Polarizing microscopy