# How is the wavelength of monochromatic light measured

how is the wavelength of monochromatic light measured by using diffraction grating and spectometer?

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## Answers and Replies

What have you found out so far?

Using diffraction grating, when incident parallel beam is at normal incidence, then emergent parallel beams are seen in directions such that
dsinθ = nλ

by considering the spacing of grating, and the order of the diffracted beams as well as the angle of diffracted beams to the normal, the wavelength may be measured.

Is it Correct?