A $4\mathrm{cm}$ tall object is placed on the principal axis of convex lens. The distance of the object from the optical centre of the lens is $12\mathrm{cm}$ and its sharp image is formed at a distance of $24\mathrm{cm}$ from it on a screen on the other side of the lens. If the object is now moved a little away from the lens, in which way (towards the lens or away from the lens) will he have to move the screen to get a sharp image of the object on it again ? How will the magnification of the image be affected?