Three complete orders on each side of the m=0 order can be produced in addition to the m=0 order.
The ruling separation is d=1/(470mm-1)
Diffraction lines occurs at an angle θ such that dsin=mλ,when λ is the wavelength and m is an integer.
Notice that for a given order,the line associated with a long wavelength is produced at a greater angle than the line associated with shorter wavelength.
we take λ to be the longest wavelength in the visible spectrum (538nm) and find the greatest integer value of m such that θ is less than 90°.
That is,find the greater integer value of m for which mλ<d.
since,d/λ
There are three complete orders on each side of the m=0 order.
The second and third orders overlap.
learn more about diffraction from here: brainly.com/question/28168352
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