Concave Mirrors and Image Formation Notes

Image Classification and Mirror Types

• Real Image: Formed when light rays actually arrive and intersect at the image location; can be projected onto a screen.

• Virtual Image: Formed by light appearing to come from a location; rays do not actually arrive at the image point.

• Concave (Converging) Mirror: A mirror reflecting on its inner curved surface, causing light rays to meet.

• Convex (Diverging) Mirror: A mirror reflecting on its outer curved surface, causing light rays to spread apart.

Anatomy of a Concave Mirror

• Centre of Curvature ($C$): The center point of the sphere from which the mirror surface is derived.

• Principal Axis: The straight line passing through the centre of curvature ($C$) to the midpoint of the mirror.

• Vertex ($V$): The specific point where the principal axis intersects the mirror surface.

• Focus ($F$): The location where incident rays parallel to the principal axis converge after reflecting off the concave mirror.

Ray Diagram Rules for Image Location

1. Parallel-Focus Ray: Draw an incident ray from the top of the object parallel to the principal axis; reflect it through the focus ($F$).

2. Focus-Parallel Ray: Draw an incident ray from the top of the object through the focus ($F$); reflect it parallel to the principal axis.

3. Convergence: The image forms where reflected rays intersect. If they do not meet, extend the rays behind the mirror to locate a virtual image.

S.A.L.T. Image Analysis

• Size ($S$): Smaller than, larger than, or the same size as the object.

• Attitude ($A$): Upright (same orientation) or inverted (upside down).

• Location ($L$): Distance or relative position compared to the mirror, $C$, or $F$.

• Type ($T$): Real or Virtual.

Summary of Image Characteristics in Concave Mirrors

• Object Beyond $C$: Image is smaller, inverted, real, and located between $C$ and $F$.

• Object At $C$: Image is the same size, inverted, real, and located at $C$.

• Object Between $C$ and $F$: Image is larger, inverted, real, and located beyond $C$.

• Object At $F$: No clear image is formed as reflected rays are parallel.

• Object Inside $F$ (Between F and Mirror): Image is larger, upright, virtual, and located behind the mirror.