Influence of Light Source Size on Interference

In this paper the effect of the extension of two coherent light sources on interference fringes is examined. The change in the aspect of the fringes when the coherent sources are widened in the same direction is discussed. A relation between the width of the coherent sources, the distance of the screen, and the wavelength for which the interference fringes may be seen, is established. This relation is discussed in connection with some special cases.