15.0 REFLECTION AT CURVED SURFACES

Reflection at curved surfaces extends the laws of reflection to mirrors that are parts of a sphere. These mirrors – concave and convex – are used in telescopes, vehicle headlights, security mirrors, and makeup mirrors. This chapter covers their properties, how to draw ray diagrams, and how to calculate image positions using the mirror formula.

15.1 TYPES OF MIRRORS

There are two main types of curved mirrors, each with a different shape and effect on light rays.

15.1.1 Concave Mirror (Converging Mirror)

• A concave mirror has a reflecting surface that curves inwards, like the inside of a spoon.
• It is called a converging mirror because parallel rays of light, after reflection, meet (converge) at a point.
• Uses: Shaving/makeup mirrors (to see an enlarged image), dentist's mirrors, reflecting telescopes, solar furnaces, and car headlights (to produce a parallel beam).

15.1.2 Convex Mirror (Diverging Mirror)

• A convex mirror has a reflecting surface that curves outwards, like the outside of a spoon.
• It is called a diverging mirror because parallel rays of light, after reflection, spread out (diverge) as if coming from a point behind the mirror.
• Uses: Rear-view mirrors in vehicles (because they give a wider field of view and always produce an upright, diminished image), security mirrors in shops, and on blind corners.

15.2 P