Curved Mirrors
Simple Explanation
A concave mirror curves inward (like the inside of a spoon) and can form either real or virtual images, depending on the object's position — it converges (brings together) reflected parallel rays at a real focal point. A convex mirror curves outward (like the back of a spoon) and always forms a virtual, upright, diminished image — it diverges (spreads out) reflected parallel rays, which only appear to come from a virtual focal point behind the mirror.
Why Do We Need It?
The type of curved mirror used depends entirely on the job needed — concave mirrors can magnify (like a shaving or makeup mirror), while convex mirrors give a wider field of view, always showing an upright (never confusingly inverted) image.
Worked Example
Choose the right type of curved mirror
A car needs a wing mirror that shows the widest possible field of view behind the car, always upright. Explain which type of curved mirror should be used, and why.
Why Does This Work?
The behavior of each mirror type comes directly from its curvature — a concave (inward-curving) surface focuses parallel rays toward a real point in front of the mirror, while a convex (outward-curving) surface spreads them apart, so they only ever appear to meet behind the mirror.
Real-Life Example
Concave mirrors in torches and telescopes
A flashlight or torch uses a curved mirror behind its bulb to produce a strong, directional beam.
Placing the bulb at the concave mirror's focal point makes the reflected rays travel out as a parallel, concentrated beam, rather than spreading out uselessly in every direction.
Practice
Which type of curved mirror always forms a virtual, upright, diminished image, no matter the object's distance?
MediumCommon mistake
Assuming a concave mirror always magnifies — a concave mirror's image depends on the object's position: it can be magnified, the same size, or diminished, and either real (inverted) or virtual (upright), unlike a convex mirror which always behaves the same way.
Quick Review
- Concave: converges rays, can form real or virtual images depending on object distance.
- Convex: diverges rays, always forms virtual, upright, diminished images.
- Convex mirrors give a wider field of view — used for car mirrors and security mirrors.