  The Young\'s modulus of a nylon string has been determined experimentally by
combining elasticity theory and wave optics. A diffraction experiment has been
setup to determine the change in the string diameter for different tensile
forces applied by means of hanging weights. A linear elasticity model has been
used to calculate the Young\'s modulus. A simple method has been provided which
could be used as the basis of an experiment for introductory university level.
