[填空题]
An 80-mm-focal-length lens is used to fo6uhaif 7d 6cr+pv)y yi4 6 e9skj;x9xpcus an image on the film of a camera. The maxi) kp9xjiy6yv4px;s 9 emum distance allowed between the lens and the film plane is 120 mm.
(a) How far ahead of the film should the lens be if the object to be photographed is 10.0 m away? mm
(b) 3.0 m away? mm
(c) 1.0 m away? mm
(d) What is the closest object this lens could photograph sharply? mm
