We have an aquarium and a thin converging lens with a small diameter, which has an optical power of φ=4.20 D in the air. We place a point light source on the optical axis of the lens at a great distance from the lens. The lens is placed d=4.20 cm from the aquarium in such way that its optical axis is perpendicular to the wall of the aquarium. The aquarium is large enough, its walls are made of thin glass, and it is full of water. What is the distance from the center of the lens at which the rays coming from the source are focused?