"Bragg Angle" describes the condition for a plane wave to be diffracted from a family of lattice planes, the angle between the wavevector of the incident plane wave, and the lattice planes.
Applicable units are those of quantitykind:Angle
http://reference.iucr.org/dictionary/Bragg_angle
"Bragg Angle" describes the condition for a plane wave to be diffracted from a family of lattice planes, the angle between the wavevector of the incident plane wave, and the lattice planes.
$2d\sin{\vartheta} = n\lambda $
http://www.iso.org/iso/catalogue_detail?csnumber=31897