# Curved Mirrors There are concave mirrors that are

• Slides: 7

Curved Mirrors • There are concave mirrors that are curved inward • And there are convex mirrors that are curved outward

2 -in-1 Curved Mirrors • A spoon offers simple examples of convex and concave mirrors • When you see yourself in the spoon try to notice the characteristics of the image you see. (Are you smaller? Are you upside down? )

• Like plane mirrors, curved mirrors also follow the laws of reflection in which: 1. Angle of incidence = Angle of reflection 2. Incident ray, reflected ray and the normal always lie on the same plane (same side). • However, when light rays strike a curved surface, each ray will reflect at a slightly different position. • For an image to be formed, all of these rays eventually have to meet at a common point, the focal point (F).

Curved Mirror Terms Light coming from object Principal axis V f F C Reflective surface Principal Axis – imaginary line drawn through the vertex perpendicular to the curved mirror’s surface Vertex (V) – middle point of a curved mirror Focal Point (F) – the point where light rays meet or appear to meet Focal Length (f) – distance from V to F Centre of Curvature (C) – the point in the centre of the sphere in which the mirror was sliced. This is equal to 2 F.

Convex Mirrors (Diverging Mirrors) • Because this mirror is curved, the reflected rays bounce at different angles depending on where they hit the mirror. Instead of collecting light rays, this mirror spreads out the rays. • A convex mirror has a focal point (F) • When light rays hit it parallel to the principal axis, the reflected rays all seem to come from the point F.

Drawing Ray Diagrams for Convex Mirrors Object Image Principal axis 1. V F C Draw the 1 st incident ray parallel to principal axis from object to surface of curved mirror. Position your ruler and draw reflected ray as though it was coming from F. 2. Draw the 2 nd incident ray as though it was going to V. Stop when the ray hits the mirror. Determine the angle of incidence and use this to determine the angle of reflection (θi = θr). Draw the reflected ray using θr from the V. 3. Draw the 3 rd incident ray as though it was going to F. Stop when the ray hits the mirror. Draw the reflected ray backwards, parallel to the principal axis. ADD THIS: Note: For #3, it can be replaced with an incident ray that appears to go to C, this ray reflects upon itself.

Image Characteristics (SALT) Object Image Principal axis • • V F S – Smaller than the object A – Upright L – Closer to the mirror than the object T – Virtual C