Q17 of 25 Page 10

The image of an object formed by a mirror is real, inverted and is of magnification -1. H the image is at a distance of 40 cm from the mirror, where is the object placed? Where would the image be if the object is moved 20 cm towards the mirror? State reason and also draw ray diagram for the new position of the object to justify your answer. ( CBSE 2016)

Given: Magnification, m = -1


Distance of image, v= -40 cm


Magnification is written as:




u=-40 cm


Since object distance is equal to the image distance and the image formed is a real image, therefore the object is placed at centre of curvature of the mirror C.


When the object is moved 20 cm towards the mirror, then the new position of the image formed will be at focus of the mirror.


Applying the mirror formula:





Now in case 2nd, when f= -20 cm


Applying the mirror formula






The ray diagram is as follows:


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