  Despite recent major advances, the opacity remains a source of substantial
uncertainty in the calculation of solar models, and hence of solar oscillation
frequencies. Hence it is of substantial interest to investigate the sensitivity
of solar structure to changes in the opacity. Furthermore, we may hope from the
precise helioseismic inferences of solar structure to obtain information about
possible corrections to the opacities used in the model calculation. Here we
carry out detailed calculations of the influence on solar models of changes in
the opacity, including also evolutionary effects. We find that over the
relevant range the response of the model is approximately linear in the opacity
change, allowing the introduction of opacity kernels relating a general opacity
change to the corresponding model changes. Changes in the convection zone can
be characterized entirely by the change in the initial composition and mixing
length required to calibrate the model.
