A concave lens of focal length 15 cm, forms an image 10 cm from the lens. How far is the object placed from the lens? Draw the ray diagram.
Focal length of the lens f = -15 cm (since concave lens are negative)
Since the image is formed on the same side, v = -10 cm.
u = ?
Using lens formula
= 
Therefore u = -30 cm
Since the image is formed on the same side, v = -10 cm.
u = ?
Using lens formula
= Therefore u = -30 cm
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