9. A parallel beam of \( X \)-rays is diffracted by rocksalt crystal the Ist order maximum being obtained when the glancing angle of incidence is 6 degree and 5 minutes. The distance between the atomic planes of the crystal is \( 2.81 \times 10^{-10} \mathrm{~m} \). Calculate the wavelength of the radiation.
(Ans. \( 0.5952 \times 10^{-10} \mathrm{~m} \) )
