Light forces induced by scattering and absorption in elastic dielectrics lead
to local density modulations and deformations. These perturbations in turn
modify light propagation in the medium and generate an intricate nonlinear
response. We generalise an analytic approach where light propagation in
one-dimensional media of inhomogeneous density is modelled as a result of
multiple scattering between polarizable slices. Using the Maxwell stress tensor
formalism we compute the local optical forces and iteratively approach
self-consistent density distributions where the elastic back-action balances
gradient- and scattering forces. For an optically trapped dielectric we derive
the nonlinear dependence of trap position, stiffness and total deformation on
the object's size and field configuration. Generally trapping is enhanced by
deformation, which exhibits a periodic change between stretching and
compression. This strongly deviates from qualitative expectations based on the
change of photon momentum of light crossing the surface of a dielectric. We
conclude that optical forces have to be treated as volumetric forces and that a
description using the change of photon momentum at the surface of a medium is
inappropriate