Light: Mirrors and Lenses
What each curved mirror shows
Compare the images in the two kinds of curved mirror.
Compare them properly (Activity 10.3). You need a concave mirror, a convex mirror, two small wooden blocks to stand them up, and a small toy.
Stand the mirrors side by side and put the toy 3 to 4 cm in front of them. Is each image bigger or smaller than the toy? The right way up? Is left and right swapped? Write it down. Then slowly move the toy away and watch, and repeat with each mirror on its own.
| Mirror | Toy close | Toy far away |
|---|---|---|
| concave | erect and enlarged | inverted: at first enlarged, then smaller and smaller |
| convex | erect and diminished (smaller) | still erect, a little smaller still |
| plane | erect, same size | erect, same size |
So curved mirrors behave quite differently from plane mirrors. In concave and convex mirrors the size of the image changes as the object moves, and in a concave mirror the image even turns upside down once the object is far enough away.
One thing is the same in all three: lateral inversion. Your left side appears as the image's right side, in plane, concave and convex mirrors alike.
So just by looking at the images, you can tell whether a mirror is plane, concave or convex.
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