Fig. (4) Photographs of diffraction patterns from Young’s double- slits taken step-by-step by moving double-slits away from laser focal point. (a) slits are 5 mm from F and thus diffraction patterns are well separated in space (b) slits at 9 mm from F shows interference fringes only in small central overlapped region and (c) slits at 25 mm from F results in superposition of individual slit diffraction patterns to generate Young’s fringes.