Ray diagrams are used to depict the image formation by tracing the path of light rays i.e. incident rays and REFLECTED rays. They are drawn in order for anyone to view a point on the image of an object. These ray diagrams depend on the position of the object.General rules for image formation using ray diagrams:Any ray of light that passes through the mirror, is always parallel to the principal axis.Any ray of light that passes through the mirror always passes through the principal focus (f) of the mirror after reflection.A ray of light passing through the center of curvature of any mirror is reflected back along the same path.Any incident ray which isn’t parallel to the principal axis is also reflected diagonally and the incident ray and the reflected ray always follow the laws of reflection i.e. the angles formed by these rays are equal to each other.Ray Diagrams for a Concave MirrorFor a concave mirror, there are six possible positions where the object can be positioned and an image is formed:a. Object is positioned at infinityWhen the object is placed at infinity, rays PQ and RS parallel to the axis are reflected from points Q and S respectively. Rays PQ and RS intersect each other and get CONVERGED at the principal focus (f). And since when the object is placed at infinity, the PROPERTIES of the images formed are highly diminished, point sized and real and inverted.b. Object is positioned between infinity and center of curvature(c)Here the object MN is placed between infinity and center of curvature (c) of a concave mirror, then a ray MP parallel to the principal axis and another ray MQ that pass through the center of curvature(c) intersect each other at M’ after reflection between focus (f) and center of curvature (c). Therefore the properties of the images formed here are that the image formation is between principal focus (f) and center of curvature (c), the image formed is diminished and real and inverted.c. Object is positioned at Center of Curvature (c)d. Object is positioned between the center of curvature (c) and principal focus (f) Object MN is placed between the center of curvature (c) and principal focus (f), then the ray MP parallel to the principal axis and another ray MQ passing through principal focus (f) intersect each other beyond the center of curvature (c) at point M’. Hence the properties of the images formed here are that the image is formed beyond the center of curvature (c), and the image is real and inverted.e. Object is positioned at principal focus (f)Object MN is positioned at the principal focus (f), then ray MP parallel to the principal axis passes through principal focus (f) giving the reflected ray PS. Second ray MQ that passes through the center of curvature is reflected along the same path giving the reflected ray QR. Here, since the rays, PS and QR become parallel to each other and therefore the image formation is at infinity. Here the properties of the images formed are highly enlarged images and real and inverted images.Explanation:The graphical method of locating the image produced by a concave mirror consists of drawing light-rays emanating from key points on the object, and finding where these rays are brought to a focus by the mirror. This task can be accomplished using just four simple rules:An incident ray which is parallel to the principal axis is reflected through the focus $F$ of the mirror.An incident ray which passes through the focus $F$ of the mirror is reflected parallel to the principal axis.An incident ray which passes through the centre of curvature $C$ of the mirror is reflected back along its own path (since it is normally incident on the mirror).An incident ray which strikes the mirror at its vertex $V$ is reflected such that its angle of INCIDENCE with respect to the principal axis is equal to its angle of reflection.The validity of these rules in the paraxial approximation is fairly self-evident.Consider an object $ST$ which is placed a distance $p$ from a concave spherical mirror, as shown in FIG. 71. For the sake of definiteness, let us suppose that the object distance $p$ is greater than the focal length $f$ of the mirror. Each point on the object is assumed to radiate light-rays in all directions. Ray Diagrams for Spherical Mirrors. This Demonstration lets you visualize the ray diagrams for concave and convex spherical mirrors. By manipulating the object and mirror locations, you can create real or virtual images. The ray parallel to the principal axis and the ray that hits the center of the mirror are drawn.