An object of size 7.0 cm is placed at 27 cm in front of a concave mirror of focal
length 18 cm. At what distance from the mirror should a screen be placed, so that
a sharp focussed image can be obtained? Find the size and the nature of the image.

NCERT Class X
Science - Science

Chapter_Light – Reflection and
Refraction

1

Answers

2015-06-02T17:34:42+05:30
Given
 Size of the object [o] = +7cm
  F = -18cm
  U= -27cm
 V = ?
 1/f = 1/v+1/u
 1/-18cm = 1/v-1/27
  1/v= -1/54 v = -54cm
Since Vis – ve screen should be placed at 54cm in front of the mirror.
Size of the image : m= I/O= -v/u I/7=-[54/27] I= -14cm
Nature of the image : image is real , inverted and magnified. 
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