Monochromatic x rays are incident on a set of NaCl crystal whose interplanar spacing is 39.8 pm. When the beam is rotated from the normal, firstorder Bragg reflection is observed. We have to find the wavelength of the x rays.

Solution: Click For PDF Version It is given that the Bragg reflection occurs when the beam is incident at an angle of from the normal to the crystal planes. Therefore, the Bragg angle will be
For the first order Bragg reflection, we have the equation
where d is the interplanar spacing. For the NaCl crystal
Therefore,
