A detailed theory of volume spin wave reflection from the randomly rou
gh surface of a ferromagnet is presented. The contribution to damping
of the reflected wave is calculated. This contribution is due to the s
cattering of the initial volume wave into secondary surface and volume
spin waves. The value of damping is proportional to the correlation l
ength and the square of the roughness amplitude. Numerical calculation
s of the attenuation rate as a function of the angle of incidence and
the ratio between the surface anisotropy and the wavenumber are provid
ed. They yield the angle of incidence where the attenuation has a maxi
mum. In analogy to optics, this angle is similar to the Brewster angle
. Numerical estimations of damping and a comparison of its value with
the ferromagnetic resonance linewidth are also made. Finally, the resu
lts of the calculation of the scattering of surface exchange spin wave
s by surface roughness are presented and discussed.