Photography A 35-mm camera has a standard lens with focal length 50 mm and can focus on objects between 45 cm and infinity.
(a) Is the lens for such a camera a concave or a convex lens?
(b) The camera is focused by rotating the lens, which moves it on the camera body and changes its distance from the film. In what range of distances between the lens and the film plane must the lens move to focus properly over the 45 cm to infinity range?