Revise: Light
Sources of light, reflection, image formation in plane and curved mirrors, and the mirror formula.
Luminous: makes its own light. Non-luminous: only reflects light.
The Moon is non-luminous — it only reflects sunlight.
Angle of incidence = angle of reflection (both from the normal).
35° incidence → 35° reflection.
Plane mirror image: virtual, upright, same size, laterally inverted.
1.8m from mirror → image 1.8m behind, 3.6m total.
Concave converges rays; convex always gives a virtual, upright, small image.
Car wing mirrors use convex mirrors for a wider view.
We see any object only because light from it enters our eyes.
A candle flame is luminous; the page it lights is not.
Regular reflection (smooth) gives sharp images; diffuse (rough) scatters light.
Wet roads reflect more like a mirror, causing glare.
A virtual image can never be projected on a screen.
Text held to a mirror looks laterally reversed.
Concave mirror's image type depends on object distance; convex never changes.
A concave mirror in a torch focuses light into a beam.
u is always negative; concave f negative, convex f positive.
f=−20, u=−50 → v≈−33.3cm.