600-nm light is incident on a diffraction grating with a ruling separation of 1.7

We will use the principle of overlap, specifically the principle of constructive interference to solve this problem. Mathematically this can be expressed as

Where,

N = Number of fringes or number of repetition of the spectrum

d = Distance between slits

Wavelength

Diffraction angle

Our values are given as

600nm

Replacing we have that the angle is,

Therefore the second order line occurs at a diffraction angle of 44.9°