Chapter 34.5, Problem 34.5TYU

When used with 35-mm film (image area 24 mm × 36 mm), a lens with f = 50 mm gives a 45° angle of view and is called a “normal lens.” When used with an electronic sensor that measures 5 mm × 5 mm, this same lens is (i) a wide-angle lens; (ii) a normal lens; (iii) a telephoto lens.