A He-Ne gas laser which produces monochromatic light of wavelength λ=6.328×10⁻⁷ m is used to calibrate a reflection grating in a spectroscope. The first-order diffraction line is found at an angle of 18.5∘ to the incident beam. How many lines per meter are imprinted on this reflecting diffraction grating?
(a) 3.40×10⁶ lines/m
(b) 5.92×10⁶ lines/m
(c) 3.40×10⁷ lines/m
(d) 5.92×10⁷ lines/m
