A He-Ne gas laser which produces monochromatic light of a known wavelength λ = 6.328 × 10−7m is used to calibrate a reflection grating in a spectroscope. The first-order diffraction line is found at an angle of 21.5° to the incident beam. How many lines per meter are there on the grating?
Step 1 of 4 ^
(the slit saparation)