A cubic crystal with interatomic spacing of 024 nm is used t

A cubic crystal with interatomic spacing of 0.24 nm is used to select gamma rays of energy 100 keV from a radioactive source containing a continuum of energies. If the incident beam is normal to the crystal, at what angle do the 100-keV gamma rays appear?

Solution

E = hc/lambda

100 keV = 100 x 10^3 x 1.6 x 10^-19 = 1.6 x 10^-14 J

lambda = hc/E

lambda = 1.2375 x 10^-11 m

sinx = n*lambbda/2d

x = 1.477 degree