  Rayleigh scattering is a result of an interaction of photons with bound
electrons. Rayleigh scattering is mostly neglected in calculations of hot star
model atmospheres because most of the hydrogen atoms are ionized and the
heavier elements have a lower abundance than hydrogen. In atmospheres of some
chemically peculiar stars, helium overabundant regions containing singly
ionized helium are present and Rayleigh scattering can be a significant opacity
source.
  We evaluate the contribution of Rayleigh scattering by neutral hydrogen and
singly ionized helium in the atmospheres of hot stars with solar composition
and in the atmospheres of helium overabundant stars. We computed several series
of model atmospheres using the TLUSTY code and emergent fluxes using the
SYNSPEC code. These models describe atmospheres of main sequence B-type stars
with different helium abundance. We used an existing grid of models for
atmospheres with solar chemical composition and we calculated an additional
grid for helium-rich stars with $N$(He)/$N$(H)=10.
  Rayleigh scattering by neutral hydrogen can be neglected in atmospheres of
hot stars, while Rayleigh scattering by singly ionized helium can be a
non-negligible opacity source in some hot stars, especially in helium-rich
stars.
