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.
Slide 3
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.
Slide 4
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).
Slide 5
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.
Slide 6
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.
Slide 7
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.
Slide 8
1. Principal Axis 2. Vertex 3. Focal Point (F) 4. Centre of
Curvature 5. Focal Length
Slide 9
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.
Slide 10
(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
Slide 11
(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
Slide 12
(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
Slide 13
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
Slide 14
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
Slide 15
iii) A ray of light going towards the principal focus will
reflect back parallel to the principal axis. V F C
