Explore the Telescope & Microscope: Compound Optics Lab
Switch between a telescope and a compound microscope, adjust the objective and eyepiece focal lengths, and watch the ray-traced image.
- Free to use
- No signup
- Nothing to install
- Runs in your browser
Illustration. Open the tool for the real thing.
See it in action
The Telescope & Microscope: Compound Optics Lab with sample data entered and the result showing.
What is the Telescope & Microscope: Compound Optics Lab?
Switch between a telescope and a compound microscope, adjust the objective and eyepiece focal lengths, and watch the ray-traced image and total magnification update live. It runs in your browser, so a change to a setting or a drag on an object shows up at once.
Astronomers size telescope eyepieces exactly this way to hit a target magnification, and biology and materials labs use compound microscopes built from exactly this two-lens design.
3 steps to your result
Open the tool and follow along. Nothing to install.
What you get
A telescope's angular magnification is M = f0/fe: a long objective focal length combined with a short eyepiece focal length gives high magnification.
A compound microscope's objective first forms a real, magnified intermediate image (found from the thin lens equation), which the eyepiece then magnifies again as a simple magnifier.
Total microscope magnification is the product of the objective's linear magnification and the eyepiece's angular magnification, M = |mo x me|.
Build a 20x telescope using the challenge.
Switch to microscope mode and move the object just outside the focal length.
Compare a short eyepiece versus a long one in telescope mode.
Used for
Pick one to see how it fits.
Physics learners
Physics students in middle school, high school and first-year university, teachers who want a quick demonstration for the projector, and anyone revising for exams.
Try it freeTeachers
For teachers: project the Telescope & Microscope: Compound Optics Lab on the board, let students predict the result, then run it together and test this: Switch to microscope mode and move the object just outside the focal length. For students: change one thing at a time and write down what changes.
Try it freeHow it compares
A plain look at this tool next to the usual alternative.
| This simulation | Textbook diagram | |
|---|---|---|
| Interactive | Drag, tap and change settings | Fixed picture |
| Install | Nothing to install | Not needed |
| Cost | Free to use | Depends on the book |
Questions people ask
Why does a telescope need a long objective and short eyepiece for high magnification?
Telescope magnification is M = f0/fe, so increasing the objective's focal length or decreasing the eyepiece's focal length both directly increase the ratio and therefore the magnification.
Why is a microscope's total magnification a product of two magnifications rather than a simple ratio?
The objective first creates a real intermediate image with its own linear magnification mo, and the eyepiece then magnifies that already-enlarged image again as a simple magnifier with angular magnification me, so the two multiply together.
Is the Telescope & Microscope: Compound Optics Lab free to use?
Yes. The Telescope & Microscope: Compound Optics Lab is free, needs no signup or download and runs in your web browser. It is part of the Physics group of AZRS simulations.
Does the Telescope & Microscope: Compound Optics Lab work on a phone or tablet?
Yes. The Telescope & Microscope: Compound Optics Lab takes touch input as well as mouse input, so you can use its 2 adjustable settings with a finger. A larger screen makes the controls and graphs easier to read.
How do I use the Telescope & Microscope: Compound Optics Lab?
1. In the Telescope & Microscope: Compound Optics Lab, use the controls to change Objective focal length f₀, Eyepiece focal length fₑ. The simulation reacts instantly. 2. In the Telescope & Microscope: Compound Optics Lab, pick an option such as Telescope, Microscope to switch modes or load an example. 3. Start with this experiment: Build a 20x telescope using the challenge. Drag any glowing handle, object or slider with your mouse or finger and the Telescope & Microscope: Compound Optics Lab responds in real time. 4. Change one setting at a time and watch which readout moves, then compare it with this idea: A telescope's angular magnification is M = f0/fe: a long objective focal length combined with a short eyepiece focal length gives high magnification.
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Try the Telescope & Microscope: Compound Optics Lab now
Switch between a telescope and a compound microscope, adjust the objective and eyepiece. Free to use.
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