The phenomenon is found to be prominent when the wavelength of light is compared with the size of the obstacle or aperture of the slit. These two experiments clearly show that when light travels past an obstacle, it does not proceed exactly along a straight path, but bends around the obstacle.
According to Huygens’s principle, each point on the rim of the sphere behaves as a source of secondary wavelets which illuminate the central region of the shadow. The shadow of the spherical object is not completely dark but has a bright spot at its centre.
Another simple experiment can be performed by exhibiting the same effect.Ĭonsider that a small and smooth ball of about 3 mm in diameter is illuminated by a point source of light.The shadow of the object is received on a screen as shown in the figure. If light travels in a straight path, the central region should appear dark i.e., the shadow of the screen between the two slits. In Young’s double-slit experiment for the interference of light, the central region of the fringe system is bright. See Also: Refraction of light Diffraction of light The convex lens is not needed to converge the spherical wavefronts.Wavefronts leaving the obstacles are also spherical.Source and screen are not far away from each other.
