A human hair is placed between the ends of two microscope slides, forming a thin wedge of air between the slides, as indicated in the figure below. An expanded He-Ne laser beam of wavelength 633 nm is incident on the slides from above. An observer viewing the slides from above sees a series of thin, straight, alternating light and dark fringes, with 113 bright fringes spread over the 4.55 cm length of the slides. Find the diameter of the hair.