---
title: "Using a Microscope"
description: "Use a light microscope correctly to prepare, focus, and examine biological specimens, including making accurate labelled drawings at an appropriate magnification"
canonical: https://lightmysky.com/learn/science/using-a-microscope-mt_lMLeNLDRO8
source: https://lightmysky.com/learn/science/using-a-microscope-mt_lMLeNLDRO8.md
retrieved: 2026-10-19
---

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# Using a Microscope

Use a light microscope correctly to prepare, focus, and examine biological specimens, including making accurate labelled drawings at an appropriate magnification

Subject: Science · Area: Organisms & Life Processes · Ages 11 to 12
Page: https://lightmysky.com/learn/science/using-a-microscope-mt_lMLeNLDRO8

## Ready when they can

- Sets up a light microscope safely and correctly (coarse focus then fine focus)
- Prepares a wet mount slide with a biological specimen (e.g. onion skin)
- Calculates the magnification of an image (magnification = image size ÷ actual size)
- Draws an accurate labelled diagram of observed cells with a scale

## Lesson: Using a Microscope

Cheek cells are too small to see clearly by eye. A school light microscope uses an eyepiece and an objective to enlarge them. Start at the lowest power. Watch the gap from the side while bringing the lens and slide closer; do not let them touch. Through the eyepiece, use coarse focus to increase the gap slowly until an image appears. Then sharpen it with fine focus. Use only fine focus at high power.

*(drawing: Find a new specimen on low power with coarse focus, then fine focus. At high power, use only fine focus.)*

**Example.** With your teacher, peel a thin inner layer from an onion. Lay it flat on a clean slide and add a drop of water. Touch one edge of a coverslip to the water, then lower the other edge slowly to reduce trapped air bubbles. Iodine stain can help cell parts stand out. Use stains only as your teacher directs.

*(drawing: Lower one edge first, then the other, to reduce air bubbles.)*

Use matching units. Magnification = image size ÷ actual size. A 9 mm drawing of a 0.03 mm cell has magnification 9 ÷ 0.03 = 900 ÷ 3 = 300. Multiplying both sizes by 100 leaves the ratio unchanged. To find image size, use image size = magnification × actual size.

Draw only the parts you observe. Use a sharp pencil and straight ruled label lines. Include a scale line (scale bar) marked with the real length it represents. Base the scale on a measurement, so the reader can work out the specimen's size.

**Recap.** Focus on low power first, mount your slide carefully, then work out and record the magnification of what you draw.

## Practice

8 questions on this page, each with its working shown.

## Needs first

- [Cells Under the Microscope](https://lightmysky.com/learn/science/cells-under-the-microscope-mt_VfA4xo4kUv)

## Opens up

- [Magnification and Scale Calculations](https://lightmysky.com/learn/science/magnification-and-scale-calculations-mt_0Iowx29ddQ)