A He-Ne Laser,which Produces Light of Wavelength 632

Multiple Choice

A He-Ne laser,which produces light of wavelength 632.8 nm,is used to calibrate a diffraction grating.If the first-order maximum occurs at 20.5° from the central spot,what is the distance between the slits of the grating?

A) 0.905 µm
B) 1.81 µm
C) 2.20 µm
D) 3.62 µm
E) 4.52 µm