Ans: 3
2071 set d q. no. 12 2069 supp set b q. no. 122069 set b
q. no. 12 a parallel beam of sodium light is incident normally
on a diffraction grating. the angle between the two first order
spectra on either side of the normal is 27°42'. assuming that
the wavelength of light is 5.893 x 10-7m, find the number of
rulings per mm on the grating?
ans: 406 lines/mm