Page 144 - NCERT Science Class 10 English Medium

(ii) A ray passing through the
principal focus of a concave
mirror or a ray which is
directed towards the
principal focus of a convex
mirror, after reflection, will
emerge parallel to the
principal axis. This is
illustrated in Fig.9.4 (a)
and (b). (a) (b)

Figure 9.4
Figure
Figure 9.49.4
Figure 9.4
(iii) A ray passing through the Figure 9.4
centre of curvature of a
concave mirror or directed
in the direction of the centre
of curvature of a convex
mirror, after reflection, is
reflected back along the
same path. This is
illustrated in Fig.9.5 (a) and
(b). The light rays come back
(a) (b)
along the same path
Figure
Figure 9.59.5
Figure
Figure 9.5
9.5
Figure 9.5
because the incident rays
fall on the mirror along the
normal to the reflecting
surface.
(iv) A ray incident obliquely to
the principal axis, towards
a point P (pole of the mirror),
on the concave mirror
[Fig. 9.6 (a)] or a convex
mirror [Fig. 9.6 (b)], is
reflected obliquely. The
incident and reflected rays
follow the laws of reflection
(a) (b)
at the point of incidence
(point P), making equal Figure 9.69.6
Figure
Figure 9.6
Figure 9.6
9.6
Figure
angles with the principal axis.
Remember that in all the above cases the laws of reflection are followed.
At the point of incidence, the incident ray is reflected in such a way that
the angle of reflection equals the angle of incidence.
(a) Image formation by Concave Mirror
Figure 9.7 illustrates the ray diagrams for the formation of image
by a concave mirror for various positions of the object.

Light – Reflection and Refraction 139

2024-25