 Mirrors that are not flat are called curved mirrors.  Depending on whether the reflective coating is on the inside or outside of the curve will decide if it is a concave or convex type of mirror.

 If the mirror is coated on the inside of the curve it is called a concave mirror.  Those which reflect from the outside of the curve are called convex mirrors.

 A curved mirror is a cut out section of a circle. In mathematics the distance from the curve to the centre of the circle is referred to as a radius (r).  For the purpose of curved mirrors, the centre of the circle is called the centre of curvature (C).

 Any circle is an example of both a concave and convex mirror. Note the solid line is the reflected surface and the hatched side is the back of the mirror.

 The principal axis is a line through the centre of curvature that strikes the mirror at a 90 o angle.  The vertex (V) of a curved mirror is where the principal axis meets the mirror.  The centre of curvature and vertex both lie along the principal axis.

 Half the distance between the centre of curvature (C) and mirror is called the focus or focal point (F).  Therefore, if the focus (F) has a distance of 4 cm from the curved mirror, the centre of curvature(C) is 8 cm.  This is why the focus is given the symbol of F and the centre of curvature is located at 2F.

1. Principal Axis 2. Vertex 3. Focal Point (F) 4. Centre of Curvature 5. Focal Length

 To determine the location of any image in a concave mirror you need to draw at least two incident rays.  The following rules will help you to draw the incident and reflected rays for objects with a concave mirror.

(i) A ray of light, which is parallel to the principal axis of the concave mirror, will reflect off of the mirror and pass through the principal focus (F) V F C

(ii) A ray of light passing through the center of curvature (C) of a concave mirror will reflect back along the same path V F C

(iii) A ray of light passing through the principal focus (F) of a concave mirror will reflect back parallel to the principal axis. V F C

i) A ray of light, which is parallel to the principal axis of a convex mirror will reflect as if it had come from the principal focus. V F C

ii) A ray of light going towards the center of curvature(C) of a convex mirror is reflected back along the same path. V F C

iii) A ray of light going towards the principal focus will reflect back parallel to the principal axis. V F C