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# SPHERICAL MIRRORS CLASS 10 CBSE NCERT

SPHERICAL MIRRORS

A reflecting mirror whose reflecting surface is curved inward or outwards is known as a spherical mirror.

CONCAVE MIRROR

The reflecting mirror whose reflecting surface is curved inwards is known as a concave mirror. The Center of the sphere of which the mirror is a part lies in front of the reflecting surface.

Pole– the center of the reflecting surface of a spherical mirror is called its pole. It is represented by the letter P.

Centre of Curvature– The reflecting surface forms a part of a sphere the center of this sphere is known as the center of curvature. It is represented by C. It is not a part of the reflecting surface.

The radius of Curvature– The radius of the sphere of which the reflecting surface of the spherical mirror forms a part is known as the radius of curvature of the spherical mirror.

Principal Axis– The straight line that joins the center of curvature and pole is called the principal axis of the mirror. It is represented by PC. Principal Axis is normal to the mirror at its pole.

Focus– The rays parallel to the principal axis after reflection from a concave mirror meet at a point on the principal axis (PC) this point is known as the focus of the mirror. It is represented by f. The distance from pole (P) to focus (f) is called the focal length of the mirror. Focal length is represented by F.

RAY DIAGRAMS OF CONCAVE MIRROR.

POSITION OF OBJECT                      POSITION OF IMAGE                    NATURE OF THE IMAGE             SIZE OF THE IMAGE

Infinity                                                                 at f                                                          real & inverted                                           point sized

Beyond C                                                     between C & f                                                  real and inverted                                       diminished

At C                                                                      At C                                                            real & inverted                            same size as that of object

Between C & F                                             beyond C                                                         real and inverted                                         magnified

At f                                                                    infinity                                                           real and inerted                                    highly magnified

Between P&f                                                  behind the mirror                                        virtual & erect                                            magnified     USES OF CONCAVE MIRROR

1. Used in torches, searchlights and vehicles headlight- because they give a powerful beam of light.
2. Used as shaving mirrors- because they show a larger image of the face.
3. Used by dentists- because they show a larger image of teeth.
4. Used in solar furnaces- to concentrate sunlight to produce heat.

CONVEX MIRROR

The reflecting mirror whose reflecting surface is curved outwards is known as a convex mirror. The center of the sphere of which the mirror is a part lies at the back of the reflecting surface.

Pole– the center of the reflecting surface of a spherical mirror is called its pole. It is represented by the letter P.

Centre of Curvature– The reflecting surface forms a part of a sphere the center of this sphere is known as the center of curvature. It is represented by C. It is not a part of the reflecting surface.

The radius of Curvature– The radius of the sphere of which the reflecting surface of the spherical mirror forms a part is known as the radius of curvature of the spherical mirror.

Principal Axis- The straight line that joins the center of curvature and pole is called the principal axis of the mirror. It is represented by PC. Principal Axis is normal to the mirror at its pole.

Focus– The rays parallel to the principal axis after reflection from a concave mirror appear to emerge from a point on the principal axis (PC) this point is known as the focus of the mirror. It is represented by f. The distance from pole (P) to focus (f) is called the focal length of the mirror. Focal length is represented by F.

RAY DIAGRAM OF CONVEX MIRROR

Position of the Object                   Position of the Image                       Nature of the Image                      Size of the Image

Infinity                                                        at f, behind the mirror                                 virtual, erect                         highly-diminished, point sized

Between infinity & pole                    between P & f, behind the mirror                     virtual, erect                                      diminished  USES OF CONVEX MIRROR

1. Rear-view mirror in vehicles- because it gives a wider field of view and they always give an erect image.

SIGN CONVENTION OF SPHERICAL MIRROR

The sign convention of the mirror is like we read a graph. Distance or position of the image since its measured horizontally is taken as the sign of the X-axis, whereas the height of the image which is vertical is taken on the Y-axis. MAGNIFICATION & MIRROR FORMULA

u= distance of an object from the mirror

v= distance of the image from the mirror

f= focal length of the mirror

The mirror formula is the relation between u,v, and f.

1/v+1/u =1/f

h= height of the object

h´= height of image                               Magnification= height of image (h´)/height of object(h)

Magnification (m)= h´/ h= −v/u

The negative sign of magnification is for real images

The positive sign of magnification indicates a virtual image.

The positive sign of height indicates an erect image

The negative sign of height indicates an inverted image.

BY

ARJOO PUNDIR