Diffraction Grating Formula

A diffraction grating defines an optical component with a periodic structure which splits the light into various beams that travel in different directions. It is an alternative way to observe spectra other than a prism. Generally, when light is incident on the grating, the split light will have maxima at an angle θ.  The formula for diffraction grating is used to calculate the angle.

Diffraction grating formula


diffraction grating formula

n = order of grating,

d = distance between two fringes or spectra

λ = wavelength of light

θ = angle to maxima

Question 1: A diffraction grating is of width 5 cm and produces a deviation of  300

in the second-order with the light of wavelength 580 nm. Find the slit spacing.


Given: Angle θ =300 , order n = 2, wavelength λ = 580 nm.

The slit spacing is given by,

diffraction grating formula 1

d = 2×580×10-9 /sin 

diffraction grating formula 3 m

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