Unit 01 · The Microscope: Parts, Care & Focusing
This is the first rung of the ladder, and every rung above it depends on this one. You learn the compound microscope by using it: naming each part and what it does, carrying and storing it without damage, setting illumination and the diaphragm for contrast, and focusing cleanly — low power first, coarse then fine, always moving away from the slide. Mastery here is not something you can explain your way into. An instructor watches you do it, and the image in the eyepiece is the proof.
| Criterion | Not yet | Approaching | Mastered |
|---|---|---|---|
| Parts & their jobs | Cannot reliably name the objectives, condenser, diaphragm, or focus knobs, or say what each does. | Names most parts but confuses coarse vs. fine focus, or what the diaphragm changes. | Names every part on sight and states its job — objectives, stage and clips, condenser, iris diaphragm, coarse and fine focus. |
| Carrying, storage & care | Grabs the scope one-handed or leaves it on high power; wipes lenses with a shirt or paper towel. | Carries and stores it correctly when reminded, but forgets to return to low power or to use lens paper. | Carries with two hands (arm and base), stores on the lowest objective with the cord wrapped, and cleans optics only with lens paper. |
| Illumination & contrast | Leaves the light at one setting and ignores the diaphragm; the image is washed out or too dark to read. | Adjusts brightness but not the diaphragm, so faint specimens stay invisible. | Sets the lamp and works the iris diaphragm to bring out contrast without glare, retuning it for each specimen. |
| Focusing procedure | Focuses down toward the slide on high power — risking a cracked slide or a scratched objective. | Starts on low power but reaches for the coarse knob on high power, or racks the wrong direction. | Starts on the lowest objective, focuses coarse-then-fine while moving away from the slide, then steps up through objectives on fine focus only. |
| Centering, scanning & the mechanical stage | Raises magnification before finding or centering the specimen and loses it off the field. | Centers on low power but drives the stage jerkily and drifts off the target. | Finds and centers the specimen on low power first, then scans smoothly with the mechanical stage as magnification climbs. |
| Integration (cross-domain) | Treats the technique as isolated steps; makes no cross-domain connection. | Names a link to history, reading, or writing but cannot defend why it matters. | Connects the skill to its anchor across History · Reading · Writing (plus chosen electives) and defends why the connection matters. |
“I carried it with a hand under the base, set it on the 4× objective, and opened the diaphragm about halfway. Then I focused up with the coarse knob until the onion skin came in and switched to fine. Only then did I go to 10× — on fine focus only — so I’d never drive a lens down into the slide.”
“I just turned the big knob until something showed up… I think I was on the biggest lens? The picture was kind of dark but I left it like that.”
You demonstrate this module by doing it — an instructor watches you carry, set up, illuminate, and focus a real scope, not a multiple-choice test. A criterion counts as mastered only when you can perform the technique cleanly and say why each step protects the instrument and sharpens the image. Mastery is demonstrated, not awarded.
A 5-page clipboard packet — unit overview, key terms, the mastery rubric, anchor examples, and a score sheet you can print and grade against.