For in 1900 all electromagnetic radiation of longer wavelengths was already known at least to the extent that one could not seek in it the more striking characteristics of X-rays such as, for example, the strong penetrating power.
For as long as one has no further point of reference, apart from the position of the maximum, the wavelength thus remains uncertain by an integral factor.
For both reasons, owing to the thermal motion and to the working together of various wavelengths, factors arise which, in a similar manner to the structural factor, exert some influence upon the brightness of the interference points but not upon their location.
