Microscope Basics and Types

Overview

This lecture introduces the basics of microscopes, covering key terms, microscope types, microscope parts, slide preparation, usage techniques, and practical tips for classroom and experimental biology.

Key Microscope Concepts

• Magnification is how much larger a microscope makes an object appear.
• Resolution is the ability to distinguish two separate objects that are very close together.
• A microscope with 0.2 micron resolution can only distinguish two objects if they are at least 0.2 microns apart.

Types of Microscopes

• Light microscopes use light to visualize specimens; common in classrooms.
• Brightfield microscopes show a darker image on a light background.
• Darkfield microscopes create bright images on a dark background by blocking the main light source.
• Phase-contrast microscopes provide detailed images of living specimens without stains.
• Electron microscopes use electron beams for higher magnification and resolution.
• Transmission Electron Microscopes (TEM) visualize internal specimen structures.
• Scanning Electron Microscopes (SEM) visualize 3D surfaces of specimens.

Parts 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.
• Objective lenses (e.g., 4x, 10x, 40x) and eyepiece lens (typically 10x) provide total magnification by multiplying their powers.
• Coarse focus knob moves the stage dramatically for general focusing.
• Fine focus knob moves the stage slightly for precise focusing.
• Stage knobs move the slide side to side.
• Arm and base allow for safe carrying.
• Power should be unplugged and the microscope covered when not in use.

Slide Preparation and Microscopy Technique

• Wet mounts are made by placing a drop of sample and a cover slip on a slide.
• Start with the scanning objective to locate the specimen, then increase magnification as needed.
• Only use lens paper to clean the lens to avoid damage.
• Adjusting light and focus patiently is important for clear images.

Safety and Best Practices

• Handle glass slides and cover slips carefully to avoid breakage.
• Avoid moving the stage too close to the objective lens to prevent crushing the slide.
• Clean only with lens paper, never regular tissue.
• Store microscope properly when done.

Applications in Biology

• Microscopes help visualize mitosis, plant structures, and osmosis in cells.
• Using stains or immersion oil can improve specimen visibility and resolution.

Key Terms & Definitions

• Magnification — The increase in apparent size of an object by a microscope.
• Resolution — The ability to distinguish two closely spaced objects as separate.
• Objective Lens — The primary lens close to the specimen that provides variable magnification.
• Eyepiece Lens — The lens you look through, also contributing to total magnification.
• Wet Mount — A slide preparation using a liquid sample and a cover slip.

Action Items / Next Steps

• Review how to perform a wet mount and practice on a classroom microscope.
• Further reading: Physics of microscope resolution and types of light microscopes (as suggested in video details).
• Explore staining techniques and the use of immersion oil at high magnifications for clearer images.