Singular surface theory is applied to study the growth and decay properties of weak magnetogasdynamic discontinuities under the intluences of thermal conduction and the time-dependent radiation field interacting with magnetogasdynamic field with finite electrical conductivity. It is shown that the time-dependent radiation field gives rise to a radiation induced weak wave which is always damped and the magnetogasdynamic waves which break at the wave front if the initial discontinuity is sufficiently strong. The wave front curvature effects on the weak magnetogasdynamic waves are also discussed.