The discover of X-rays aroused the interest of all physicists, and many joined in the investigation of their properties. In 1899 Haga and Wind performed a single slit diffraction experiment with X-rays which showed that X-rays are a wave motion phenomenon, and from the size of the diffration pattern, their wavelength could be estimated to be 10 cm. In 1906 Barkla proved that the waves are transverse by showing that they can be polarized by scattering from many materials