As per the question,
A large number of narrow rectangular slits having width in the order of the wave length of light and arranged side by side with equal opaque spaces is called a plane transmission diffraction grating. It is an extension of diffraction due to double slit.
wavelength of wave is given (λ)=577nm
m=3
We know that dsinθ=mλ
⇒dsinθ=577×10−9×3m
⇒dsinθ=1731×10−9m
dsinθ=1.731×10−6m
dsinθ=1.731μm
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