Another property is the way that it can converge the rays to its focal
point. This is extensively used in many places. Look at the shape of TV
dish antennas.
If you look around you will see many curved surfaces but all surfaces
are not concave, many of these are convex.
Have you observed the rare view mirrors of a car?
What type of surface do they have?
raw ray diagrams for convex surfaces?
Have you observed images formed on the rear and
window glasses of a car? What type of surfaces are
these? See figure -16.
Can we draw ray diagrams for convex surfaces?
Rays diagram of convex mirror
One can draw ray diagrams for a convex mirror too. The ‘easy’ rays
that we identified earlier can be used in this case with small modification.
Here there are three rules which describe these rays. The procedure for
drawing the diagram is similar and is not repeated here.
Rule 1: A ray parallel to the axis, on meeting the
convex mirror will get reflected so as to appear as if
it is coming from the focal point. See figure-17.
Rule 2: This is converse of Rule 1. A ray travelling in
the direction of the focal point, after reflection, will
become parallel to the axis. See figure-18.
Rule 3: A ray travelling in the direction of the
centre of curvature will, on reflection, travel in the
opposite direction and appears to be coming from
the centre of curvature. See figure-19.
Have you observed images formed on the rear and
window glasses of a car? What type of surfaces are
these? See figure -16.
Can we draw ray diagrams for convex surfaces?
Rule 2: This is converse of Rule 1. A ray travelling in
the direction of the focal point, after reflection, will
become parallel to the axis. See figure-18.
Rule 3: A ray travelling in the direction of the
centre of curvature will, on reflection, travel in the
opposite direction and appears to be coming from
the centre of curvature. See figure-19.
