PE-0400 Diffraction of Light

All objects which restrict the free propagation of light cause diffraction. Although this phenomenon is always present, it is usually neglected, because the effect is too insignificant for the topic of investigation. But if light hits sharp edges, diffraction will appear clearly and cannot be neglected, especially when light is diffracted on very narrow openings like holes or slits. Christian Huygens formulated his observation of diffraction in the 17th century applying the principle of elementary waves. In 1800 Fresnel and Fraunhofer both studied the effect of diffraction in detail. Fresnel used divergent light for his investigations, whereas Fraunhofer used parallel light created by a pair of lenses. Both techniques are termed as Fresnel and Fraunhofer diffraction respectively. This experiment offers both types of diffraction. Experiments are performed using monochromatic laser light which will be diffracted at slits and holes of various widths. Thin wires impressively proves the Babinet theorem which states that complementary masks (slit, wire) result in the same diffraction pattern. The obtained diffraction patterns are imaged on a white screen and the pattern can also be recorded by a CCD camera.