Walker, Halliday & Resnick — Diffraction: Problem 66

66 Manufacturers of wire (and other objects of small dimension) sometimes use a laser to continually monitor the thickness of the product. The wire intercepts the laser beam, producing a diffraction pattern like that of a single slit of the same width as the wire diameter (Fig. 36-42). Suppose a helium–neon laser, of wavelength 632.8 nm, illuminates a wire, and the diffraction pattern appears on a screen at distance L = 2.60 m. If the desired wire diameter is 1.56 mm, what is the observed distance between the two tenth-order minima (one on each side of the central maximum)?