Uses of concave mirrors Given the type of images concave mirrors produce, they have many uses.
• All virtual images produced by concave mirrors are magnified and upright. This means that concave mirrors are ideal for vanity mirrors, shaving mirrors and dentist’s mirrors (Fig. 13.10).
• All light rays coming from the focal point are reflected parallel to the principal axis. Therefore, placing an illuminated source such as a strong bulb at the focal point of a concave mirror produces a collimated (parallel) beam of light suitable for floodlights or searchlights (Fig. 13.11).
• Concave mirrors can be used to capture the light needed in a projector.
Convex mirrors
While you do not have to study convex mirrors in as much detail for the Leaving Certificate Physics course, you need to be able to draw the formation of an image. This requires the rules of reflection in a convex mirror.
Rules of reflection in a convex mirror C
F FIG. 13.12
2. Any incoming ray directed towards the focal point will be reflected parallel to the principal axis (Fig. 13.13).
F C
1. Any incoming ray that hits the pole is reflected at an angle r equal to the size of angle i (Fig. 13.12). The principal axis can be considered as the normal because it is perpendicular to the mirror surface.
FIG. 13.10 A dentist’s mirror uses a concave mirror to produce a magnified, upright image
FIG. 13.11 A collimated beam can be used for floodlights
