Optics
Convex mirror — virtual image
A convex mirror always makes a reduced, upright, virtual image behind it.
Convex mirror — virtual image — interactive Optics simulation. A convex mirror always makes a reduced, upright, virtual image behind it. Free browser-based virtual physics lab with live SI measurements and a guided tutorial.
Convex mirror
A convex mirror always makes a reduced, upright, virtual image behind it.
Convex mirrors always diverge reflected rays, producing virtual upright images smaller than the object. The wide field of view makes them standard for vehicle side mirrors and hallway safety mirrors despite reduced magnification.
- Virtual upright image
- m < 1
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
A convex (bulging outward) mirror has a negative focal length by convention, the same way a diverging lens does. Does it ever form a real, enlarged image?
Predictions to weigh
- It can form a real image if the object is close enough.
- No — like a diverging lens, a convex mirror always forms a reduced, upright virtual image, regardless of object distance.
- It always forms an enlarged image.
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 convex-virtual preset and press Reset. The mirror's focal length is fixed at −15 cm.
- Enable the image-distance and magnification readouts.
- Set the object distance for each trial and record the image distance and magnification.
Governing equation
Convex Mirror Imaging — dᵢ = dₒ·f/(dₒ − f)
A convex (diverging) mirror has negative focal length by convention. Substituting f < 0 into the mirror equation always produces a virtual image with 0 < m < 1, exactly like a diverging lens.
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 = −15 cm, then m = −d_i/d_o. Compare both to the table.
- Explain why a convex mirror's negative focal length guarantees a virtual, reduced image at every object distance — mirroring (pun intended) the diverging-lens experiment's behavior exactly.
Where this shows up beyond the lab
- Convex mirrors are used for store security mirrors and passenger-side car mirrors ('objects in mirror are closer than they appear') precisely because they show a wide field of view at reduced size. Explain, using your magnification data, why that wording on car mirrors is necessary.
- Compare this experiment's magnification values to the concave-real experiment's, at similar object distances. Explain why a convex mirror's reduced image is fundamentally different from a concave mirror's enlarged (or inverted) one.
- AP Physics 2 — Unit 13: Geometric Optics
- General High School Physics — Light & optics
- NGSS High School Physics — Wave properties
- Welcome to Convex Virtual
- Select the object
- Press Play
- Virtual mirror image
- 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.