Mirrors with Jobs
Concave or convex? Match the mirror to the mission
What this lesson covers
Why it matters
The dentist, the bus driver, the lighthouse keeper and the solar-cooker chef all shopped at the same mirror store — and none of them could swap purchases without disaster.
The idea in plain words
The mirror job board. Tap the postings.
concave concentrates · convex surveys
Why does the solar cooker's pot sit at the mirror's focus?
F is where the sunlight queue converges — lunch at the focal point
- job 1: dentist / shaving — concave with the object INSIDE F: erect, magnified view
- job 2: torch / headlight — concave with the bulb AT F: parallel beam to the horizon
- job 3: solar cooker — concave facing the Sun: parallel rays concentrated AT F — the pot sits there
- job 4: rear-view / street corner — convex: wide-angle, always-erect surveillance
- Sun's rays arrive parallel
- Parallel rays reflect THROUGH F — all the energy lands on one pot
Predict first
Why do vehicles use CONVEX rear-view mirrors instead of plane ones?
A convex mirror shrinks the world into the frame — you see three lanes, not one. The price: 'objects are closer than they appear.'
- convex gives a much WIDER field of view (erect, though diminished) — correct
- convex magnifies the traffic
- convex is cheaper to make
What you do
Give each professional the right mirror — and the right object position where it matters.
Check yourself
'Objects in mirror are closer than they appear' is printed on convex mirrors because…
Small image reads as 'far away' to your brain — the warning recalibrates you.
A dentist holds the concave mirror…
Inside F is the only zone giving an upright MAGNIFIED image — anything else shows the tooth upside-down.
To distinguish plane, concave and convex mirrors without touching, look at your image and…
The classic identification question — your own face is the test kit.
- the diminished image tricks your distance judgement — correct
- the mirror physically moves objects
- it's a legal joke
- closer to the tooth than its focal length — correct
- beyond C
- exactly at F
- bring your face close: plane = same size; concave = magnified; convex = diminished — correct
- measure their weight
- impossible without instruments