A diffraction grating 1.0 cm wide has 400 lines per millimeter and is used in the first order to analyze a monochromatic laser beam. The research team wants to double the resolving power R of the setup while leaving the wavelength and order number unchanged. Which of the following changes would most effectively achieve this goal?
a) Use a grating that has 200linesmm−1 but keep the same illuminated width.
b) Replace the laser with one whose wavelength is twice as large.
c) Illuminate the grating with a beam that is 2.0cm wide.
d) Observe the second–order diffraction maximum instead of the first.