The size of the image formed by a convex mirror of focal length 30 cm is a quarter of the size of the real object. Then the distance of the object from the mirror is a) 30cm b) 90cm c) 120cm d) 60cm plz justify the answer !

Asked by Prashant Jawla | 27th Oct, 2012, 06:45: PM

Expert Answer:

ans (b) 90 cm
Focal length = +30 cm
The distance between the object and the mirror (u) = ?
The distance between the image and the mirror (v) = ?
Let the size of the object be equal to 1.
Given size of the image = 1/4 size of the object.

ho = 1



But we know that















u = -90 cm

The distance of the object from the mirror = 90 cm

Answered by  | 27th Oct, 2012, 07:53: PM

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