Engineering Physics

14.10 Plane diffraction grating [Diffraction at n slits]

A large number of narrow rectangular slits having width in the order of the wave length of light and arranged side by side with equal opaque spaces is called a plane transmission diffraction grating. It is an extension of diffraction due to double slit. The first diffraction grating constructed by Fraunhofer consists of a large number of parallel wires of 0.05 mm diameter and they are separated by 0.0533 mm to 0.687 mm. A plane transmission grating can be easily constructed by drawing a large number of closely spaced lines on a plane transparent plate like glass with a sharp diamond point. The lines on the plate are opaque to light and the spaces between these lines are transparent. Usually ...