Overview
This lecture introduces the basics of microscopy, covering key concepts such as magnification and resolution, types of microscopes, microscope parts, and practical tips for using and caring for microscopes.
Key Concepts of Microscopy
- Magnification is how much larger a microscope makes an object appear compared to its actual size.
- Resolution is the ability to distinguish between two separate objects under the microscope.
- Good resolution is needed to tell close objects apart as distinct.
Types of Microscopes
- Light microscopes use visible light to view specimens and are common in classrooms.
- Brightfield microscopes show dark images on a light background.
- Darkfield microscopes block direct light to highlight structures by making them appear bright on a dark background.
- Phase-contrast microscopes can visualize living specimens in detail without staining.
- Electron microscopes use electron beams for much higher magnification and resolution.
- Transmission Electron Microscopes (TEM) show internal structures; Scanning Electron Microscopes (SEM) show 3D surfaces.
Parts and Functions of a Compound Light Microscope
- Light source illuminates the specimen.
- Condenser lens focuses light on the specimen.
- Diaphragm adjusts light intensity.
- Stage holds the slide; stage clips secure it; stage knobs move it side-to-side.
- Objective lenses (scanning, low power, high power) offer different magnifications.
- Eyepiece lens further magnifies the image.
- Total magnification = objective lens power x eyepiece lens power.
- Coarse focus knob makes large adjustments; fine focus knob makes precise adjustments.
- Arm and base are for carrying and stability.
Practical Use and Care
- Prepare slides using a wet mount with cover slips.
- Start at lowest magnification and focus before increasing power.
- Handle slides carefully to avoid breakage.
- Use lens paper (not tissue) to clean lenses.
- After use, remove the slide, turn off the light, lower the stage, set to lowest power lens, unplug, and cover the microscope.
Applications of Microscopy
- Observe mitosis in onion root tips, plant stomata, and osmosis in plant cells.
- Staining and immersion oil are advanced techniques for better visualization and resolution.
Key Terms & Definitions
- Magnification — How much larger an object appears under the microscope.
- Resolution — Ability to distinguish two closely spaced objects as separate.
- Objective Lens — Lens close to the specimen, provides primary magnification.
- Eyepiece Lens — Lens you look through, provides secondary magnification.
- Wet Mount — Slide preparation method using liquid and a cover slip.
Action Items / Next Steps
- Read provided links for more on microscope types and the physics of resolution.
- Practice preparing and viewing slides using classroom microscopes.
- Try observing common specimens, such as pond water or plant cells, under the microscope.