CBSE Class 10 Science 2017 · Paper 31/1/C · Question 19

Laws of reflection, which hold for spherical mirrors as for plane mirrors: (1) The angle of incidence is equal to the angle of reflection. (2) The incident ray, the normal to the mirror at the point of incidence and the reflected ray all lie in the same plane. At a spherical mirror the normal at any point is the radius through that point, which passes through the centre of curvature. Ray diagram: from the top $A$ of the object, a ray parallel to the principal axis is reflected so that it appears to come from the principal focus $F$ behind the mirror, and a ray directed towards the centre of curvature $C$ is reflected back along its own path. The reflected rays diverge; produced backwards, they meet behind the mirror between $P$ and $F$, where the image $A^{\prime }{B}^{\prime }$ is formed (see the figure). Characteristics: the image is virtual and erect. (It is also diminished, and it lies behind the mirror between $P$ and $F$.) Use: convex mirrors are used as rear-view (wing) mirrors in vehicles. They always give an erect, though diminished, image, and being curved outwards they have a wider field of view than a plane mirror, so the driver can see a much larger area of the traffic behind.