Engineering Physics

14.11 Grating spectrum

The diffraction pattern formed with a grating is known as a grating spectrum. From equation (14.4), (e + b) sin θ = ± nλ, n = 0, 1, 2, 3, … we know the θ values for different principal maxima. If the number of lines in the grating are very large then the maxima are sharp and bright. Lines parallel to the grating lines called spectral lines. Different order bright lines are formed on both sides of central maximum. Instead of monochromatic light if white light is used, then light of different wave lengths are diffracted in different directions for each order of diffraction as shown in Fig. 14.17.

 

Figure 14.17 Grating spectrum for white light source

The central image is white because the central maxima of different wave ...