Page 38 - Physics 10_Float

GEOMETRICAL OPTICS

Types of Reflection Incident
Nature of reflection depends on smoothness of the surface. rays Reflected rays
For example, a smooth surface of silver reflects rays of light in
one direction only. The reflection by these smooth surfaces is
called regular reflection (Fig.12.2). Most of the objects in
everyday world are not smooth on the microscopic level. The Smooth surface
rough surfaces of these objects reflect the rays of light in Fig. 12.2: Regular reflection
many directions. Such type of reflection is called irregular
reflection (Fig. 12.3).
Incident
Reflected rays
12.2 SPHERICAL MIRRORS rays
A mirror whose polished, reflecting surface is a part of a
hollow sphere of glass or plastic is called a spherical mirror. In
a spherical mirror, one of the two curved surfaces is coated Rough surface
with a thin layer of silver followed by a coating of red lead Fig. 12.3: Irregular reflection
oxide paint. Thus, one side of the spherical mirror is opaque
and the other side is a highly polished reflecting surface.
Depending upon the nature of reflecting surface, there are For Your Information
two types of spherical mirrors as shown in Fig.12.4.
Aperture or opening Radius of
Mirror
curvature
Centre of Aperture
curvature R
Principal axis Principal axis R
C C Light rays are reflected in a
Pole plane mirror, causing us to see
Pole
an inverted image.
(a) Concave mirror (b) Convex mirror Do you know?
Fig. 12.4: Types of spherical mirrors
Concave Mirror: A spherical mirror whose inner curved surface
Image
is reflecting is called concave mirror. In concave mirror the size
of the image depends on the position of the object. Both virtual
and real images can be formed by a concave mirror.
Convex Mirror: A spherical mirror whose outer curved surface Mirror
is reflecting is called convex mirror. In convex mirror the size of Real
the image is always smaller than the object. Only virtual and object
erect image is formed by a convex mirror.
Pole: It is the midpoint of the curved surface of spherical The image you see in a flat
mirror is at the same distance
mirror. It is also called vertex.
behind the mirror as you are in
Centre of Curvature (C): A spherical mirror is a part of a front of it.

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