The angle dependency in FCPM

Assuming the transition dipole moments for absorption and emission are parallel to the long axis of dye molecules and the excitation light is linearly polarized, the absorbed light intensity is given by

Assuming further that the rotational relaxation time of the dye is slow compared to the lifetime of the excited state, the orientation of dye during re-emittance of light can be considered identical to the orientation during absorption.  The detectable light intensity is then given by

With follows

In consequence, the detectable light intensity scales with the angle between the excitation light and the transition dipole moment over the relation