Light microscope diagram: parts and how to use one
A light microscope uses visible light and lenses to show a magnified image of a small object. The eyepiece and objective lenses enlarge the image. A stage holds the slide, and focus knobs bring the specimen into view. Explore the labelled diagram to learn what each part does.
Parts of a light microscope
The eyepiece is the lens you look through. The objective lenses sit close to the slide. Turning the nosepiece changes which objective is in use.
The stage supports the slide. Clips hold it in place while light passes through the specimen. A lamp shines light upwards. Some microscopes use a mirror to direct light instead.
The arm supports the upper parts. The base supports the whole instrument. When carrying a microscope, hold the arm with one hand and support the base with the other.
Try naming each part in the Microscope Parts game.
How to focus a slide
Put the microscope on a steady surface. Place the slide on the stage and secure it with the clips. Switch on the lamp or adjust the mirror as your teacher directs. Never point a mirror at the Sun.
Turn the nosepiece until the lowest power objective clicks into place. Look from the side as you move the stage and lens close together. Stop before they touch. Look through the eyepiece. Slowly use coarse focus to move the lens away from the slide. Stop when an image comes into view.
Use the fine focus to sharpen the image. Centre the part you want to see before moving to a higher power. At higher power, use the fine focus only. Follow your teacher's instructions for the microscope in front of you.
A thin specimen lets light pass through. You can compare what you see with the animal cell diagram and the plant cell diagram. The diagrams show structures, but a school microscope may not reveal every one.
Working out total magnification
Multiply the eyepiece magnification by the objective magnification. The result tells you how many times the microscope enlarges the image. Magnification is a ratio, so it has no unit.
This differs from measuring an image on paper. The magnification formula links image size to real size. In Magnification Challenge you can practise that calculation and unit changes.
Light and electron microscopes
A light microscope uses visible light. An electron microscope uses a beam of electrons. Electron microscopes can have much higher magnification and resolution than light microscopes. Resolution means the ability to distinguish two close points as separate.
A bigger image alone does not guarantee more detail. If two points cannot be resolved, enlarging their image will not separate them.
A light microscope can show living cells. An electron microscope keeps its specimen in a vacuum, so the specimen cannot be alive. Return to the biology hub for more cell topics.
What courses cover
At KS3, pupils use a light microscope to observe and record cell structure. AQA GCSE Biology covers the higher magnification and resolving power of electron microscopes.
OCR Gateway Biology includes the lenses, stage and lamp of a light microscope. Pearson Edexcel Biology includes using a microscope and calculating magnification. Your teacher can tell you which parts your course needs.
Worked examples
total magnification
- Multiply the eyepiece magnification by the objective magnification: 10 × 4.
×40
Common mistakes
- Adding the two lens magnifications. Multiply them to find the total.
- Using coarse focus at high power. Use fine focus to reduce the risk of hitting the slide.
- Moving the lens towards the slide while looking through the eyepiece. Watch from the side so you can stop before they touch.
- Treating magnification and resolution as the same thing. A larger image may still lack detail.
Test the labels in Microscope Parts after exploring the diagram.
Questions people ask
What does a light microscope do?
It uses visible light and lenses to make a magnified image of a small specimen, such as cells on a slide.
Why start with the lowest power objective?
It gives a wider view, making the specimen easier to find and centre before you increase magnification.
How do you calculate total magnification?
Multiply the eyepiece magnification by the objective magnification. The result has no unit.
What is the difference between magnification and resolution?
Magnification describes how much bigger the image is. Resolution describes whether two close points can be seen separately.