17. In a Michelson interferometer, one arm is 55.0 cm long and is enclosed in a box that can be evacuated. Initially, the box contains air, which is gradually pumped out, causing a change in the optical path length in that arm. During the evacuation process, 520 bright fringes pass by a point in the viewer. The interferometer uses light with a wavelength of 600 nm. What is the refractive index of air? (A) 1.000293 (B) 1.000162 (C) 1.000096 (D) 1.00028 (E) 1.00006