The following is the process of Xiaoli and Xiaomei exploring the imaging law of convex lenses: (1) Before the exploration, Xiaoli adjusted three convex lenses to the sunlight respectively.

(1) The length of optical bench is about 100cm. If a convex lens with a focal length of 48cm is used for the experiment, the required length of the experiment is at least 4×48cm= 192cm, which is longer than that of optical bench, and the operation is inconvenient. If a convex lens with a focal length of 15cm is used for the experiment, the length required for the experiment should be at least 4× 15cm=60cm, which is less than the length of optical bench, and the equipment is suitable; If a convex lens with a focal length of 4cm is used for the experiment, the length required for the experiment should be at least 4×4cm= 16cm. Although this length is smaller than that of optical bench, the experimental range is relatively small and it is not easy to operate the experiment. Therefore, a convex lens with a focal length of 15cm is selected.

(2) In the experiment, in order to make the centers of the candle, convex lens and light screen approximately at the same height, a section of candle should be cut off to make the image in the center of the light screen;

(3) In order to make the light screen accept the image of candle flame, the order of candle flame, light screen and convex lens on the table is candle, convex lens and light screen, so the convex lens is in the middle;

(4) The focal length of the convex lens is 15cm, the object distance is 12cm, and u < f, which is an upright magnified virtual image. The optical screen can't accept virtual images, so the optical screen can't accept real images at any position.

(5) When the convex lens becomes a virtual image, the object image is on the same side of the convex lens, so the eyes should observe the candle through the convex lens on one side of the screen, so the arrangement order is candle, lens and eye.

So the answer is: (1) The focal length of convex lens is too large or too small, which is not convenient for operating experiments; (2) Make the centers of the candle, the convex lens and the light screen approximately at the same height, and make the image at the center of the light screen; (3) convex lens; (4) When the object distance is less than the focal length, the convex lens becomes a virtual image, and the virtual image cannot be presented on the screen; (5) candles, lenses and eyes;