THE DIFFRACTION GRATING
    It is a thin foil with a plenty of very small gaps (up to 1000 per 1 mm). The gaps are all of the same size and uniformly arranged. They cause diffraction ("cambering") of the beam of light passing through (see the picture below). Focused by a lens, beams can undergo an interference producing interference-diffraction pattern on the screen.


THE DISCOVERY AND RESEARCH OF X RAYS