The Distance Between the Ruled Lines on a Diffraction Grating

Multiple Choice

The distance between the ruled lines on a diffraction grating is 1,900 nm.The grating is illuminated at normal incidence with a parallel beam of white light in the 400 nm to 700 nm wavelength band.What is the angular width of the gap between the first order spectrum and the second order spectrum?

A) 3.3°
B) 4.3°
C) 5.3°
D) 6.3°
E) 2.3°