ABSTRACT
Light propagates in a straight line through space. This is one of
the well-known features of light. However, this description is true
only when the space is uniform and there is no obstacle to hinder
its propagation. If there is an obstacle, light will go round it and
will diffusely propagate with extending propagation direction. This
phenomenon is known as diffraction, which is one of the typical wave natures of light. The diffraction of light is familiar even in our
daily life: When the sunlight goes though a narrow crack of a wall,
one will notice that the size of a light spot casting on a floor is
not the same as that of the crack, but is much larger than it. If one
holds two pencils in contact up to the light, a few dark lines will be
noticed between them. These phenomena are typical indications of
the diffraction of light.
