Although we have discussed single$-$slit diffraction only for a slit, a similar result hoids 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 $632\mathrm{.}4$ nm was shone on a single strand of hair, and the diffracted light was viewed on a screen $1\mathrm{.}35$ m away, the first dark fringes on either side of the central bright spot were $5\mathrm{.}30$ cm apart.