In the early days of X-ray crystallography there was an urgent need to know the wavelengths of X-rays. One technique was to measure the diffraction angle from a mechanically ruled grating. Another method was to estimate the separation of Justice Planes from the measured density of a crystal. The density of NaCl is 2.17 g cm-1 and the (100) reflection using PdKa radiation occurred at 6.0°. Calculate the wavelength of the X-rays.