Therefore, the wavelength of light will ne 146.7 nano meter. In this formula, \(\theta\) is the angle of emergence at which a wavelength will be bright. This is known as the DIFFRACTION GRATING EQUATION. Constructive interference will occur if the difference in their two path lengths is an integral multiple of their wavelength \(\lambda\) i.e., The formula for diffraction grating:Ĭonsider two rays that emerge making the angle \(\theta\) with the straight through the line. Diffraction is an alternative way to observe spectra other than a prism. where m 0,1.,k and k is a smaller integer. This is one of the reasons why transmission gratings are often designed with a lower line. containing a metallic reflector, can be achieved over a wide range of angles of incidence, it is more difficult to obtain low reflection losses of a transmission grating over a large angular range. Also, if peaks fall on peaks and valleys fall on valleys consistently, then the light is made brighter at that point. 1 Ti Tr d +- +- 1 2 Monochromatic Beam 2 1 Figure 1: Monochromatic beam incident on (blazed) diraction grating at angle iand diracted at angle r. While a high reflectance of a reflection grating, e.g. If a peak falls on a valley consistently, then the waves cancel and no light exists at that point.
Here Huygens’ Principle is applicable.Īccording to it every point on a wavefront acts as a new source, and each transparent slit becomes a new source so cylindrical wavefront spread out from each.
Rays and wavefront form an orthogonal set so the wavefront will be perpendicular to the rays and parallel to the grating. 2 Solved Examples Diffraction Grating Formula Concept of the diffraction gratingĪ parallel bundle of the rays will fall on the grating.
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