Diffraction Grating

Q.What is diffraction?

A.The process by which a beam of light or other system of waves is spread out as a result of passing through a narrow aperture or across an edge, typically accompanied by interference between the wave forms produced.

Q.What is diffraction grating?

A.It is an optically flat glass plate on which large number of equidistant parallel lines are ruled by a fine diamond pen.

Q.What is grating element?

A.It is the distance between the centers of any two successive ruled lines or transparent stripes.

Q.What is the difference between prism and grating spectrum?

A.In grating spectrum violet color is least deviated and red color is most deviated but in prism the reverse is true.

Q.When will the even order spectra disappear?

A.They will disappear if the size of opaque lines and transparent stripes is made equal.

Q.Why does red color deviate the most in case of grating?

A.This is so because in case of grating sin θ=n λ/(e+d) i.e angle of diffraction is proportional to the wavelength and the wavelength of red is maximum.

Q.What gives a more intense spectrum – prism or grating?

A. A prism gives more intense spectrum because in prism entire light is concentrated into one spectrum while in the case of grating light is distributed in the grating spectra of different orders.

Q.Why is light incident on the side of grating which has no rulings?

A.To avoid refraction of  diffracted light.

Q.Define dispersion of light.

A.The process of splitting of white light into it’s constituent colors is called dispersion of light.

Q.Describe essential parts of spectrometer.

A. Collimator , prism table,telescope.

Q.Why do we need two vernier scales?

A.To remove the error in reading due to not coinciding the axis of prism table and telescope.

Q.Name two types of spectra.

A. Emission spectra,Absorption spectra

Diffraction Grating



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