Human vision normally covers an angle of roughly 40° horizontally. A "normal" camera lens then is defined as follows: When focused on a distant horizontal object which subtends an angle of 40°, the lens produces an image that extends across the full horizontal extent of the camera's light-recording medium (film or electronic sensor). Determine the focal length f of the "normal" lens for the following types of cameras:

(a) A 35-mm camera that records images on film 36 mm wide;

(b) A digital camera that records images on a charge-coupled device (CCD) 1.60 cm wide.