The correct option is D 20 cm away from lens.
Object distance from the lens, u=−40 cm
Image distance from the lens, v=40 cm
Image distance is equal to the object distance. This happens when object is at 2f distance from the lens.
When the object is moved 10 cm towards the lens, new object distance is:
Applying lens formula, the new image distance v′ is
Shift in image is:
Thus, the image shift is 20 cm away from the convex lens.