Page 145 - Science Class 07

v Image is formed at the centre of curvature Ÿ real
in front of concave mirror. Ÿ inverted

v If the object lies between the focus (F) and Ÿ enlarged , i.e., larger than the object
the centre of curvature (C) , the image is-
v Image is formed at infinity, infront of
Ÿ real, i.e., can be obtained on the screen
concave mirror.
Ÿ inverted, i.e., upside down
Thus, we see that the posi ons and the sizes of
Ÿ enlarged, i.e., large than the object the images formed by concave mirrors depends

v The image is formed beyond the centre of on distance of the object from the pole of the
curvature but not at infinity in front of mirror. The following table sums up the
mirror. features of the images formed by concave
v If the object is located at focus (F), the mirrors.

image formed is—

Loca on of Object Loca on of Image Nature of Image Size of Image

Between P & F Behind the mirror Unreal, Erect Enlarged
Between F & C Beyond the C Real, Inverted Enlarged

At C At C self Real, Inverted Equal

Beyond C Between C & F Real, Inverted Smaller
At F Behind the mirror Erect, Unreal Enlarged

Real Image v Its size depends on type of the mirror–
v It can be obtained on a screen. equal in a plane mirror, smaller and larger
in a concave mirror.
v It is always inverted (either upside down or
sideways). USES OF CONCAVE MIRRORS

v It is formed on the same side of the mirror v Concave mirrors are used as shaving mirror.
as the object. If you place your face between the pole
and principal focus on the concave mirror,
v Its size depends on the distance of the
an erect, enlarged and virtual image of
object from P equal when at C, smaller
your face can be seen behind the mirror.
when it is beyond C, larger if between F
and C. v Head lights of automobiles are made by
concave mirror which acts as a reflector. In
Unreal Image
head lights the bulb is placed at the
v It can’t be obtained on a screen. principal focus on the concave reflector so
v It is always upright, i.e., its correct end is as to get a powerful parallel beam of light.
always up. v Den sts use concave mirrors, to see back

v It is always formed on the back side of the the tooth by placing it behind the tooth. In
mirror.

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