**To Measure the wavelength of monochromatic light**

**Diagram**

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**Formula: ****n****λ**** = d Sin****θ****. ****n=fringe order . d=diffracion grating. ****θ****=angle of diffraction **

d=500 lines per mm. Then d for formula = 1/500,000 = 2x10^{-6 }m.

**Spectrometer setup**: Focus telescope on distant object. Ensure base & stage are level, Adjust slit width.

**Errors** =Crosshairs in centre of ray? Error Vernier scales, diffraction grating not completly perpendicular to stage.

**Accuracy** = The smaller the gap in the D.G the larger the diffraction and the lower the percentage error when measuring the angles.