What is Concave mirror?
A concave spherical mirror has a reflecting surface that curves inward like the inside of a bowl. Parallel rays near the principal axis reflect toward the focal point.
What is Convex mirror?
A convex spherical mirror has a reflecting surface that bulges outward. Reflected rays diverge and appear to originate from a virtual focal point behind the mirror.
Concave mirror vs Convex mirror: comparison table
| Point of comparison | Concave mirror | Convex mirror |
|---|---|---|
| Surface | Curves inward | Bulges outward |
| Optical action | Converging | Diverging |
| Focus | Real focus in front of mirror for parallel paraxial rays | Virtual focus behind mirror |
| Image possibilities | Real/inverted or virtual/upright depending object distance | Virtual, upright and diminished for real objects |
| Field of view | Narrower for comparable size | Wider |
| Common uses | Makeup/shaving mirrors, reflectors, telescopes | Vehicle side/rear-view applications, security mirrors |
Similarities
- Both obey the law of reflection.
- Both can be approximated as sections of a sphere in basic optics.
- Both have a principal axis, pole and focal-length description in the spherical approximation.
Practical examples
- A close face in a concave makeup mirror can appear enlarged and upright when inside the focal length.
- A convex security mirror shows a wide area but makes objects appear smaller.
How to distinguish them in practice
Start with the defining biological, chemical or physical principle, then use the table to connect that principle to observable consequences.
Common mistakes to avoid
- Memorizing a single difference without understanding the underlying structure or process.
- Treating a classroom simplification as a rule with no exceptions.
- Mixing levels of comparison, such as comparing a structure on one side with a process on the other.
- Using an unlabeled diagram or definition without checking standard scientific terminology.
Frequently asked questions
Which mirror can form a real image?
A concave mirror can form a real image when the object is beyond the focal point.
Why are convex mirrors used for wide viewing?
Their diverging geometry provides a wider field of view.
Is a concave mirror always magnifying?
No. Magnification depends on object distance; it can also produce diminished real images.
Do convex mirrors have a real focus?
No for parallel incident rays; the reflected rays appear to diverge from a virtual focus behind the mirror.
Bottom line
The most useful first check is surface: Concave mirror — Curves inward; Convex mirror — Bulges outward.
Sources and further reading
KnowDifferences Editorial Team
Independent explanations with definitions, practical examples and references. Read our editorial approach.