Solve this please...

Q. A student focussed the image of a candle flame on a white screen using a convex lens. He noted down the position of the candle, screen and the lens as under

   Position of candle = 12.0 cm

   Position of convex lens = 50.0 cm

   Position of the screen = 88.0 cm

   (i) What is the focal length of the convex lens?

   (ii) Where will the image be formed if he shifts the candle towards the lens 

Dear student,
First part of the question is done correctly by Nabiha Rehan.
As the object distance and image distance are same, the image is formed at the center of curvature, or 2f
2f=38or f=19cm

(ii) As the object distance is not specific, it could be anywhere between f and 2f, then image is formed beyond 2f
            at f  then the image is formed at infinity
            or between pole and f , then the image formed is virtual and formed beyond 2f
Please refer to the figure below

Image result for image formation in convex lens


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I hope this is I m not sure about the second part...

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F is 19 cm
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