Meet the microscope
The eyepiece and objective lenses magnify the image. The stage supports the slide, the light source illuminates it and the diaphragm controls the light passing through.
The microscope
Use magnification and careful observation to study small structures.
Class notes
Open PDF →Find the specimen safely
Place and secure the slide. Begin with the lowest-power objective and follow your teacher’s focusing procedure. Use fine focus to sharpen the image; use fine focus only at higher power.
Magnification and field of view
Total magnification = eyepiece magnification × objective magnification. The field of view is the area visible through the eyepiece; as magnification increases, the visible area generally gets smaller.
Explore the idea
INTERACTIVE · MICROSCOPE MATH
Build the magnification
Choose the two lenses. Multiply their powers to find total magnification.
As magnification increases, the field of view generally becomes smaller.
01Eyepiece and objective
Light passes through lenses that magnify an image. Start with the lowest-power objective.
02Total magnification
Multiply the eyepiece magnification by the objective magnification.
03Focus and field of view
Use coarse focus at low power, then fine focus; follow your teacher’s instrument instructions.
Watch: How to use a light microscope · Amoeba Sisters
Use magnification and careful observation to study small structures.
Open on YouTube →A 10× eyepiece and 40× objective are in use. What is the total magnification?
Reveal the reasoning
10 × 40 = 400×. A larger magnification does not automatically mean a clearer image.
Try it yourself.
A microscope has a 10× eyepiece and a 40× objective. What is the total magnification?
Check your thinking
10 × 40 = 400×. Start at low power to locate the specimen before switching objectives.
Common question: Does a larger image always show more detail?
No. An image can be magnified without becoming clearer if the microscope cannot resolve the detail.
Take it further.
With a 10× eyepiece, what objective produces 100× total magnification?
See a possible explanation
A 10× objective: 10 × 10 = 100×.