A physics problem. Thank you very much.

The principle of the camera is that the camera actually uses the imaging principle of the convex lens. A convex lens, let the focal length be f (the convex lens can converge light, the point where the light converges is called the focal point, and the distance from the focal point to the center of the convex lens is the focal length), and the object distance (the distance from the object to the center of the convex lens) be u, then when u >; 2f. Put an opaque object on the other side of the convex lens, which is called a light screen in physics. On the light screen, you can get an image exactly like the real thing, but this image is inverted and reduced.

So choose one