10.2 Images in Spherical Mirrors
A plane mirror is boringly reliable: the image is always erect and the same size. Spherical mirrors are full of surprises — and the surprise depends on how far away the object is.
Activity 10.3 — Watch the image change Stand a concave and a convex mirror upright and put an object close to each, then slowly move it away, watching the images.
What Each Mirror Does - Concave mirror: with the object close, the image is erect and enlarged. As the object moves away, the image flips to inverted, and shrinks from enlarged down to small. - Convex mirror: the image is always erect and diminished (smaller), shrinking slightly more as the object moves away. - Plane mirror: always erect and the same size.
(All three show lateral inversion — left and right swapped.) So you can tell a mirror’s type just from the image it forms!
Pick a mirror and an object distance, and predict the image with the tool below.
Where we use them
Concave Mirrors at Work Concave mirrors gather and focus light, so they’re used as reflectors behind a torch bulb and car/scooter headlights (to throw a strong beam), as the magnifying dentist’s mirror (an enlarged view of teeth held close), and as the big main mirror in reflecting telescopes.
Convex Mirrors at Work Convex mirrors always give a small, upright image and show a wide area, so they’re used as vehicle side-view mirrors, road-safety mirrors at blind corners, and shop/surveillance mirrors. That’s also why side mirrors warn “Objects in mirror are closer than they appear” — the diminished image fools us into thinking traffic is farther away than it is.