Overview
This lecture introduces microscopes, focusing on essential terms, types of microscopes, components of a typical light microscope, and basic slide preparation and care techniques.
Key Concepts: Magnification and Resolution
- Magnification is how much larger a microscope makes an image appear.
- Resolution is the ability to distinguish between two separate objects under the microscope.
- Objects must be a minimum distance apart (defined by the resolution) to appear as distinct.
Types of Microscopes
- Light microscopes are commonly used in classrooms and utilize light to visualize specimens.
- Brightfield microscopes show dark images on a light background.
- Darkfield microscopes use a light stop to create light images on a dark background.
- Phase-contrast microscopes provide detailed images of living specimens without staining.
- Electron microscopes use electron beams for very high magnification and resolution.
- Transmission Electron Microscopes (TEM) visualize internal structures.
- Scanning Electron Microscopes (SEM) visualize 3D surfaces of specimens.
Parts and Functions of a Compound Light Microscope
- Compound microscopes have two sets of lenses: objective and eyepiece.
- Objective lenses typically offer different magnifications (e.g., 4x, 10x, 40x).
- Eyepiece lens also magnifies, often 10x.
- Total magnification = objective lens magnification Ă— eyepiece magnification.
- The condenser lens focuses light onto the specimen.
- The diaphragm adjusts light intensity.
- Stage holds the slide in place, often with stage clips or knobs.
- Coarse focus knob adjusts stage height quickly; fine focus knob makes precise adjustments.
- The microscope arm and base are used for safe handling.
Slide Preparation and Viewing Tips
- Wet mount slides are prepared by placing drops of specimen on a slide and covering with a cover slip.
- Avoid air bubbles when making wet mounts; they can be mistaken for organisms.
- Always start focusing with the lowest objective lens.
- Adjust light intensity for optimal image quality.
- Clean lenses only with lens paper to avoid scratches.
Handling and Safety Tips
- Glass slides and cover slips break easily; handle with care.
- Avoid raising stage too close to the objective to prevent breaking slides.
- Remove the slide, turn off light, lower stage, return lowest power lens, unplug, and cover microscope after use.
Key Terms & Definitions
- Magnification — The degree to which the image of a specimen is enlarged.
- Resolution — The minimum distance between two objects at which they can still be distinguished as separate.
- Light Microscope — A microscope that uses visible light to illuminate specimens.
- Electron Microscope — A microscope that visualizes specimens using electron beams.
- Objective Lens — The main lens that determines the initial magnification.
- Eyepiece Lens — The lens you look through; further magnifies the image.
- Wet Mount — A method of preparing slides using liquid specimens and a cover slip.
Action Items / Next Steps
- Explore further reading on microscope physics and advanced types.
- Practice preparing wet mount slides and identifying common errors like air bubbles.
- Review microscope care and cleaning procedures.
- Investigate how microscopes can aid in studying biological processes like mitosis, osmosis, and plant anatomy.