Light is incident normally on a diffraction grating through which the first order diffraction is seen at 320. The second order diffraction will be seen at

For a grating  (e+d)sinθn=nλwhere  (e+d)= grating element sinθn=nλ(e+d)For n=1,    sinθ1=λ(e+d)=sin32°This is more than 0.5. Now  sinθ2 will be more than  2×0.5, which is not possible.