Segmentally flexible macromolecules are composed of a few rigid subunits joined by semiflexible joints. When such macromolecules are exposed to an external agent, they become oriented and deformed, and this fact can be monitored by birefringence, and scattering. In this paper, we present a theoretical treatment of deformation and scattering of segmentally flexible macromolecules in an external agent that complements existing treatments of birefringence. We treat in detail the case in which the external agent is an electric field, particularizing for the case of a macromolecule with two cylindrically symmetric subunits. We focus on the steady-state behavior of the molecule in the field, studying the effect of arbitrarily high field strengths, which can be simulated using a Monte Carlo procedure. We show how the dependence of birefringence and deformation on field strength can be related to the electrooptical properties of the macromolecule and its flexibility. Particular attention is paid to macromolecular deformation expressed in term of the gyration tensor, whose components can be determined from separate scattering experiments with different scattering geometries. A joint discussion of deformations and birefringence provides a nexus between the techniques of electric birefringence and electric-field light scattering.