(2) Ming used the convex lens to do the image of an experiment, put the candle to the position of 15cm from the convex lens, that is, the object is exactly at 1 times the focal length, the candle is at the position of 15cm from the convex lens. The object is exactly between 1 times the focal length and 2 times the focal length, so at this time on the light screen into an inverted, magnified solid image;
(3) remove the glasses Ming observe the image, from the light screen is very close to the image of the candle flame, that is to say, Ming is nearsighted, should be corrected with a concave lens, so his glasses are concave;
The answer is: (1) 10.0; (2) magnification; (3) concave. (3) concave.