Comparison of prism and grating spectra.pptx

This PPT explains about the Comparison of prism and grating spectra

1. Comparison of prism and grating spectra

2. Prism spectrum 1.A prism produces only one spectrum 2.all the light energy emerging from a prism is concentrated in a single spectrum. So the intensities of spectral lines are large Grating spectrum 1.A grating gives a number of spectra of different orders on each side of the central maximum 2.in a grating most of the is concentrated in te centre maximum and the rest is distributed in the spectra of different orders.so the intensities of spectral lines are very small

3. 3.The prism spectrum is prodused by dispersion,Disperision is due to different velocities of light through the prism for different wavelengths 4.In a prism the deviation is least for red greatest for violet colour 5.The prism spectrum depends on the material of the prism 3.The grating spectrum is formed by diffraction of light .For maximum intensity the angle of diffraction is different for different wavelengths 4.In a grating the deviationis least for violet and greatest for red 5.The grating spectra are independent on the material of the grating

4. 6.The dispersive power of a prism is DS/ dY α 1/Y^3 Thus there is greater dispersion in the violet region (short wave lengths) than in the red region.The spectrum obtained with a prism is irrational spectrum 7.The resolving power of a prism is small .Hence usually the prism spectrum does not show spectrum does not show the fine structure of spectral lines 6.the dispersive power of a grating is d0/ dY =n/( a+b )cos0 It is a constant foe a particular order .Thus the spectral lines are evenly distributed.the spectrum obtained is said to be normal 7.the resolving power of the grating is large Hence the grating spectrum shows te fine structure of spectral lines

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