Q27 of 84 Page 322

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

According to the question;

Object distance (u) = -27cm;


Focal length (f) = -18cm;


Image distance = v;


By mirror formula;






⇒


⇒ v = -54cm.


Thus, screen should be placed 54cm in front of the mirror to obtain the sharp focused image.


Height of object h1= 7cm;


Magnification = =


Putting values of v and u


Magnification =


⇒


⇒ h2 = 7 ×-2 = -14.


Height of image is 14 cm.


Negative sign means image is real and inverted.


Thus real, inverted image of 14cm size is formed.


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