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?

Question

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?

richyw · Answer

I don't really get what normal means in this situation. does it mean normal to the "flat" (D=d) planes? if so I don't see how it would do anything besides go right through or relect back at angle pi