For a particular grating, the distance between adjacent slits is $2.0 \times {10^{ - 6}}{\text{ m}}$. Determine, for light of wavelength 520 nm, the maximum theoretical order of diffraction.

$n = \left( {\frac{d}{\lambda } = } \right){\text{ }}\left( {\frac{{2.0 \times {{10}^{ - 6}}}}{{5.2 \times {{10}^{ - 7}}}} = } \right){\text{ 3.85}}$;

so $\max  = 3$;

The application of the formula in part (b) was often done well.