Optics
Magnifier (object inside f)
Object inside f: an enlarged, upright, virtual image — the simple magnifier.
Magnifier (object inside f) — interactive Optics simulation. Object inside f: an enlarged, upright, virtual image — the simple magnifier. Free browser-based virtual physics lab with live SI measurements and a guided tutorial.
Simple magnifier
Object inside f: an enlarged, upright, virtual image — the simple magnifier.
A converging lens with the object closer than the focal length cannot form a real image; instead rays diverge as if from a virtual source on the same side as the object. The eye interprets these extensions as an upright, magnified image—the principle of a simple magnifier and loupe.
- M = N/f
- Virtual upright image
Investigation brief
Plan the question before you open the lab
The brief mirrors the prerendered page: driving question, competing predictions, variable roles, governing laws, setup, analysis and extension prompts remain visible and in this order.
Driving question
An object sits closer to a converging lens than its focal length. Does the lens still form a real image, or something different?
Predictions to weigh
- It still forms a real image, just farther away.
- It forms an enlarged, upright virtual image on the same side as the object — a magnifying glass.
- No image forms at all inside the focal length.
Variable roles
What you set:
- Object distance d_o (cm)
What you measure:
- Image distance d_i (cm)
- Magnification m
How the investigation runs
- Open the magnifier preset and press Reset. The lens's focal length is fixed at 10 cm.
- Enable the image-distance and magnification readouts.
- Set the object distance for each trial (always less than the focal length) and record the image distance and magnification.
Governing equation
Virtual Image Magnification — m = −dᵢ/dₒ
When an object sits inside a converging lens's focal length, the image distance d_i comes out negative (virtual, same side as the object), and the magnification m = −d_i/d_o comes out positive and greater than 1 — an upright, enlarged image, the basis of a magnifying glass.
What the printable worksheet asks students to work out
- For one trial, compute d_i from 1/f = 1/d_o + 1/d_i using f = 10 cm, then m = −d_i/d_o. Compare both to the table.
- Every trial gives negative d_i and positive m greater than 1. Explain what a negative image distance means (virtual image, same side as the object) and why m is positive here instead of negative.
Where this shows up beyond the lab
- Your data shows moving the object closer to the lens (smaller d_o, always under f) increases the magnification. Explain why a magnifying glass held very close to a small object shows it bigger than holding it farther away (but still inside f).
- What would happen to the image (and magnification) if the object were placed exactly at the focal length, d_o = f? Compare to the focal-point experiment's result.
- AP Physics 2 — Unit 13: Geometric Optics
- General High School Physics — Light & optics
- NGSS High School Physics — Wave properties
- Welcome to Magnifier
- Select the object
- Press Play
- Angular magnification
- Open the Properties panel
- You did it!
Open the interactive simulation to build the scene, press Play, and explore with live measurements and a guided tutorial.