Diagram (labeled microscope)
The labels A–M mark common parts of a microscope used in biology labs. The same names apply to most compound light microscopes, although exact shapes vary by model.
Step 1: Identify the parts of a microscope
Label key: A–M correspond to standard microscope components and their functions in focusing and image formation.
| Label | Part name | Main function | Biology lab note |
|---|---|---|---|
| A | Eyepiece (ocular lens) | Provides the final magnification for viewing. | Commonly 10×; some microscopes also have 15×. |
| B | Head / body tube | Holds the optical path between ocular and objectives. | Keeps lenses aligned for a clear image. |
| C | Revolving nosepiece (turret) | Holds objectives and rotates to change magnification. | Click-stops help center the objective over the specimen. |
| D | Objective lenses | Primary magnification and resolution of the image. | Typical set: 4× (scanning), 10× (low), 40× (high-dry), 100× (oil). |
| E | Stage | Platform supporting the slide. | Center the specimen over the stage opening for illumination. |
| F | Stage clips / mechanical stage | Holds and moves the slide precisely in X–Y directions. | Use small movements at high magnification to avoid losing the field. |
| G | Condenser | Focuses light onto the specimen. | Proper condenser height improves contrast and resolution. |
| H | Iris diaphragm | Controls the amount and cone angle of light entering the condenser. | Closing slightly increases contrast; too closed reduces resolution. |
| I | Illuminator (lamp) | Light source for transmitted-light microscopy. | Brightness is adjusted to avoid glare and improve detail. |
| J | Coarse focus knob | Moves stage (or objective) rapidly for rough focus. | Use at low magnification first to prevent slide–objective contact. |
| K | Fine focus knob | Moves stage (or objective) slowly for sharp focus. | Primary focusing control at 40× and above. |
| L | Arm | Supports the upper components; used for safe carrying. | Carry with one hand on the arm and one under the base. |
| M | Base | Stabilizes the microscope and houses the illuminator electronics. | A stable base reduces vibration artifacts at high magnification. |
Step 2: Calculate total magnification
Total magnification for a compound light microscope is the product of the ocular lens magnification and the selected objective lens magnification.
\[ M_{\text{total}} = M_{\text{ocular}} \cdot M_{\text{objective}} \]
Given \(M_{\text{ocular}}=10\), compute \(M_{\text{total}}\) for each objective.
- With the 4× objective: \[ M_{\text{total}} = 10 \cdot 4 = 40 \]
- With the 10× objective: \[ M_{\text{total}} = 10 \cdot 10 = 100 \]
- With the 40× objective: \[ M_{\text{total}} = 10 \cdot 40 = 400 \]
| Ocular | Objective | Total magnification |
|---|---|---|
| 10× | 4× | 40× |
| 10× | 10× | 100× |
| 10× | 40× | 400× |
Practical checkpoint for biology specimens
Start focusing at 40× total magnification (10× ocular with 4× objective) to locate the specimen, then increase magnification and use fine focus for sharp cellular detail. Adjusting the condenser and iris diaphragm improves contrast for unstained or lightly stained cells.