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Spherical Convex Mirrors


Convex mirrors are also curved mirrors but the silvered surface bulges outward instead of inward as with the concave spherical mirror. As with all mirrors, the angle of incidence of a ray of light is equal to the angle of reflection with respect to a normal on the surface. On a curved surface the normal changes with the curvature.

Therefore, the light rays will diverge from the object. If the rays of light are extrapolated back to the point where they converge, this will be the point where the image is formed.

For reflections off a convex mirror, the image is virtual and upright.

reflection off a convex spherical mirror
Figure 1. Reflection off a convex spherical mirror
Flash Animation: a concave circular section mirror

Use of Convex Mirrors

Convex mirrors are often used in car wing-mirrors because they have a greater field of view than a similar plane mirror. However the greater field of view is at the expense of making objects seem further away than they are in reality. Hence the expression seen etched on to the mirrors, 'Objects in Mirror are Closer than they Appear'. If you can get some extra car wing-mirrors from a car donations facility, it's a great thing to study. Concave mirrors are also used as security mirrors as they enable the viewer to see over a greater region of space.