If a laser is directed at a thin wire or hair, a diffraction pattern will occur similar to that...

If a laser is directed at a thin wire or hair, a diffraction pattern will occur similar to that produced by a slit of the same width. If the distance from the thin object to the screen on which the diffraction pattern is cast is known, a measurement of the spacing between peaks in the diffraction pattern can be used to determine the object’s width. This method is used in the wire-making industry to monitor the production of wire with a uniform width. A hair is placed a distance L =1.2 m away from a screen as shown in Figure P25.57A and illuminated with a green 532-nm laser pointer. The resulting diffraction pattern is shown in Figure P25.57B, where the distance to the first dark fringe is d =1.4 cm. What is the diameter of the hair?

 Figure P25.57