Light: Mirrors and Lenses
Where these mirrors are used
See why each kind of mirror is chosen for its job, from torches to headlights.
Once you know what each mirror does, you can see why each is picked for its job.
| Concave mirrors | Why |
|---|---|
| reflectors in torches and the headlights of cars and scooters | they gather the light and send it forward in a beam instead of letting it spread everywhere |
| a dentist's small dental mirror | held close to the teeth, it shows them enlarged |
| the main mirror of most modern reflecting telescopes | a large concave mirror (you met telescopes in Beyond Earth, Grade 6) |
| Convex mirrors | Why |
|---|---|
| side-view mirrors on vehicles | always an erect image of the traffic behind, and a much wider view of the road |
| at road bends and crossings | drivers can see traffic coming from the other side, which prevents accidents |
| in big shops | one mirror lets staff watch a large area, which discourages theft |
Why is a convex mirror so good on a vehicle? Because it curves outwards, it shows a much wider stretch of road than a flat mirror of the same size: more road in the same piece of glass.
But its image is smaller than the real cars. A small-looking car seems farther away than it really is. That's why side mirrors carry the warning: *Objects in mirror are closer than they appear.*
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