A student shines a green laser of wavelength 532 nm532\text{ nm}532 nm normally at a diffraction grating. On a screen far from the grating, the total angular separation between the two second-order (n=2n = 2n=2) maxima is measured to be 72.0∘72.0^\circ72.0∘.
What is the number of lines per mm on this diffraction grating?
5.5×1025.5 \times 10^25.5×102
8.9×1028.9 \times 10^28.9×102
1.1×1031.1 \times 10^31.1×103
5.5×1055.5 \times 10^55.5×105
