Q. 214.8( 5 Votes )
A concave lens has focal length of 20 cm. At what distance from the lens a 5 cm tall object be placed so that it forms an image at 15 cm from the lens? Also calculate the size of the image formed.
According to the question;
Object distance = u;
Image distance (v) = -15cm;
Focal length = -20cm
By lens formula;
⇒ u = -60cm.
Therefore, object is placed at 60 cm in front of lens.
Height of object h1= 5cm;
Magnification = =
Putting values of v and u
Height of image is 1.25 cm.
Positive sign means image is virtual.
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