Although we have discussed single-slit diffraction only for a slit, a similar result holds when light bends around a straight, thin object, such as a strand of hair. In that case, a is the width of the strand. From actual laboratory measurements on a human hair, it was found that when a beam of light of wavelength 632. 8 nm was shone on a single strand of hair, and the diffracted light was viewed on a screen 1. 25 m away, the first dark fringes on either side of the central bright spot were 5. 22 cm apart.