A beam of bright red light of wavelength 700 nm passes through a diffraction grating. Enclosing the space beyond the grating is a large semicylindrical screen centered on the grating, with its axis parallel to the slits in the grating. Fifteen bright spots appear on the screen.
(a) Find the maximum possible value for the slit separation in the diffraction grating.
(b) Find the minimum possible value for the slit separation in the diffraction grating.