Types and Uses of Mirrors

Aug 31, 2025

Overview

This lecture explains the three main types of mirrors—plane, concave, and convex—detailing their properties, uses, and key terms related to spherical mirrors.

Types of Mirrors

  • There are three types of mirrors: plane, concave, and convex.
  • Plane mirrors have flat surfaces and show images of the same height and upright.
  • Concave mirrors are curved inward (like the inside of a spoon) and can show inverted or magnified images depending on distance.
  • Convex mirrors are curved outward (like the back of a spoon) and always show smaller, upright, and diminished images.

Daily Uses of Mirrors

  • Plane mirrors are used for general reflection, such as in bathrooms and elevators.
  • Concave mirrors are used as shaving mirrors and can magnify faces.
  • Convex mirrors are used for rearview and side mirrors in vehicles and at road intersections for a wider field of view.

Spherical Mirrors: Structure and Function

  • Spherical mirrors are sections of a sphere and include both concave and convex mirrors.
  • Concave mirrors have a shiny, hollowed surface; convex mirrors have a shiny, bulging surface.
  • Concave mirrors converge (focus) parallel light rays to a point (converging mirror).
  • Convex mirrors diverge parallel light rays outward (diverging mirror).
  • The laws of reflection apply equally to both plane and spherical mirrors; the curvature causes their differing behaviors.

Important Terms for Spherical Mirrors

  • Center of curvature (C): Center of the sphere from which the mirror is a part.
  • Pole (P): Center of the mirror's surface.
  • Radius of curvature (R): Radius of the sphere that forms the mirror.
  • Principal axis: Straight line through the center of curvature and pole.
  • Aperture: The part of the mirror that reflects light.
  • Focus (F): Point where reflected rays converge (concave) or appear to diverge from (convex).
  • Focal length (f): Distance between the pole and focus, f = R/2.

Key Terms & Definitions

  • Plane mirror — Flat mirror reflecting upright images of the same size.
  • Concave mirror — Curved inward, forms real or magnified images.
  • Convex mirror — Curved outward, forms upright, diminished images.
  • Center of curvature (C) — The geometric center of the sphere.
  • Pole (P) — The midpoint of the mirror surface.
  • Principal axis — Main line passing through C and P.
  • Focus (F) — Point where rays converge/diverge.
  • Focal length (f) — P to F distance, equal to half the radius of curvature.

Action Items / Next Steps

  • Identify and observe different types of mirrors in your daily life (e.g., torch, dentist's mirror, street mirrors).
  • Answer the three top questions from the lecture.
  • Review labeled diagrams of concave and convex mirrors.