Overview
This lecture covers the main parts and functions of a binocular parfocal compound light microscope, including magnification concepts and how each component works.
Types and Characteristics of Microscopes
- A binocular microscope has two eyepieces for viewing.
- Parfocal means once one objective lens is focused, others will remain nearly focused when rotated.
- Compound microscopes use multiple lens systems for higher magnification.
- Light microscopes use visible light as the illumination source, limiting their maximum resolution.
Major Parts of the Microscope
- Eyepiece (ocular lens) provides 10x, 20x, or 25x magnification, most commonly 10x.
- Revolving nosepiece allows switching between objective lenses.
- Objective lenses typically include: scanning (4x), low-power (10x), high dry (40x), and oil immersion (100x).
- Total magnification equals objective lens magnification multiplied by eyepiece magnification (e.g., 100x objective × 10x eyepiece = 1,000x).
Focusing and Stage Controls
- Coarse focus knob moves the stage up or down significantly for general focusing.
- Fine focus knob moves the stage in small increments for precise focusing.
- Stage is where the specimen slide is placed and held by stage clamps.
Illumination and Light Control
- Illuminator is the built-in light source; uses visible light for viewing.
- Condenser lens focuses light onto the specimen.
- Diaphragm adjusts the amount of light passing through the specimen and stage.
Key Terms & Definitions
- Binocular — Two eyepieces for simultaneous viewing with both eyes.
- Parfocal — Lenses stay focused when switching objectives after initial focusing.
- Compound microscope — Microscope with more than one lens system for magnification.
- Objective lens — Lenses closest to the specimen, each with a specific magnification.
- Ocular lens (eyepiece) — Lens you look through; further magnifies the image.
- Coarse focus knob — Moves stage largely for rough focusing.
- Fine focus knob — Moves stage slightly for fine-tuning the image.
- Illuminator — Light source for viewing specimens.
- Condenser — Focuses light onto the specimen.
- Diaphragm — Regulates the amount of light passing through the specimen.
Action Items / Next Steps
- Review microscope part labels and magnification calculations.
- Practice focusing using both coarse and fine adjustment knobs.
- Prepare for identification of parts and their functions on a physical microscope.