DEFINITIONS
.
REFLECTION OF LIGHT
When light rays traveling is a medium reaches the boundary of other medium,
they turn back to the first medium. This phenomenon of turning back of light into
the same medium after striking the boundary of other medium is called Reflection
of Light.
LAWS OF REFLECTION
1. The angle of incident is equal to the angle of reflection i.e.
2. The incident ray, the reflected ray and the normal lie on the same plane.
REGULAR REFLECTION
When a beam pass of parallel light rays is incident on a smooth and plane
surface, the reflected rays will also be parallel. This type of reflection is called
Regular Reflection.
IRREGULAR REFLECTION
When a beam of parallel light rays is scattered in all directions. Therefore the
parallel rays incident on the surface will reflect in different directions. This type of
reflection is called "Irregular or Diffuse Reflection".
CENTER OF CURVATURE
Center of curvature of a lens or mirror is defined as the center of the sphere of
which the less or mirror is a part. C = Center of curvature.
RADIUS OF CURVATURE
Radius of curvature is the radius of sphere of which the lens or mirror is a part.
PC = Radius of curvature
OR
PC = R
POLE
For latest information , free computer courses and high impact notes visit
www.citycollegiate.com The middle or center point of a lens or a mirror is called
"Pole" P = Pole.
PRINCIPLE AXIS
The straight line joining the center of curvature to the pole is called Principle Axis.
.
PRINCIPLE FOCUS
When a narrow beam of light, parallel to the principle axis and closed to it, is
incident on the surface of a mirror or lens, the beam reflected or refracted is
converged at a fixed point on the axis. This point is called Principle Axis.
F = principle focus.
FOCAL LENGTH
The distance between the pole of a lens or mirror to the principal focus is called
Focal Length (PF) of lens or mirror. Focal length is always equal to half of the
radius of curvature of lens or mirror. f = R/2. Write down the characteristics
of image formed by a plane mirror
1. Image formed by plane mirror is laterally inverted. This means that right side of
the object appears on the left side.
2. Size of image formed by plane mirror is the same as that of size of object.
3. The image formed by plane mirror is virtual because it can not be obtained on
the screen.
4. The image is as far behind the mirror as the object is in front of the mirror. Fig.
DEFINE SPHERICAL MIRROR
AND IT'S TWO TYPES
SPHERICAL MIRROR
Mirror obtained from a spherical surface is known as Spherical Mirror. A spherical
mirror is considered as a section of hollow sphere.
TYPES OF SPHERICAL MIRRORS
There are two types of spherical mirrors.
1. Concave mirror.
2. Convex mirror.
CONCAVE MIRROR
If the inner side of the surface of a spherical mirror is polished to reflect light,
the mirror is called a Concave Mirror. Concave mirror converges parallel beam of
light.
CONVEX MIRROR
If the outer side of the surface of a spherical mirror is polished to reflect light the
mirror is called a Convex Mirror. Convex mirror diverges parallel beam light.
MAGNIFICATION
Magnification of a mirror or lens is defined as the ratio of the size of image to the
size of object.
M = height of image/height of object
M = hi/ho
or
M = q/P
REFRACTIVE INDEX
Refractive index is defined as the ratio of sine of the angle of incidence of the
sine of the angle of refraction. FORMULA :
= sine< i/ sine< r
note :Refractive index depends upon the nature of material.
It has no unit.
ANGLE OF DEVIATION
The angle at which the light ray is refracted (bend) in a prism is called angle of
deviation. It is denoted by < D. Minimum value of angle of deviation is called
angle of minimum deviation. It is denoted by