Diffraction Grating: Wavelength from sin θ = mλ/d
For a known line density 1/d, record diffraction orders m and sin θ, fit sin θ vs m; λ = d·(slope).
Goal
Find λ of the line from the grating relation.
Equipment
- 300 lines/mm grating (sim)
Theory
sin θ_m = m λ / d, so sin θ is linear in m with slope λ/d.
Procedure
- Set order m; read θ with noise. Repeat for m = 1…4.
- Fit sin θ vs m; λ = d·slope, d = 1/300 mm here.
Experiment
Conclusion
λ is consistent with the green line.