The lens is convex, as it forms real image. As mentioned in the second case, the image distance (v) is increasing; hence, the object distance (u) is decreasing. The lens formula is 1F=1v-1u⇒F=uvu-v For convex lens, object distance = -u Image distance = + v ⇒F=uvu+v where F is the focal length of the lens. Therefore, F is lesser for the second lens of focal length F2. Hence, F1 > F2 Hence, the correct option is C.