RAY DIAGRAMS OF SPHERICAL MIRRORS

We can understand the position of image and its features by means of ray diagrams. For this purpose, we take into consideration only two rays from among the many rays of light starting from a point on the object.

How do we draw the path of the reflected ray of light that incident on a spherical mirror?

We can draw the reflected rays of light incident at different points of a concave mirror or convex mirror based on the laws of reflection

•  A ray parallel to the principal axis, after reflection, will pass through the principal focus in case of a concave mirror (Fig 1(a)) or appear to diverge from the principal focus  in case of a convex mirror (Fig 1(b)). 

Fig 1

•   A ray passing through the principle focus of a concave mirror (Fig 2 (a)) or a ray which is directed towards the main focus of a  convex mirror (Fig 2(b)), after reflection, will emerge parallel to the principal axis. 

Fig 2

• A ray passing through the centre of  curvature of a concave mirror (Fig 3(a)) or directed in the direction of the centre of curvature of a convex mirror (Fig 3(b)), after reflection, is reflected back along the same path.The light rays come back along the same path because the incident rays fall on the mirror along the normal to the reflecting surface.
  

Fig 3

         

• A ray incident obliquely to the principal axis, towards a point P (pole of the mirror), on the concave mirror (Fig 4(a))  or a convex mirror (Fig 4(b)), is reflected obliquely. The incident and reflected rays follow the laws of    reflection at the point of incidence (point P), making equal angles with the principal axis.    
  
                                                             

Fig 4